Date   
12MHz xtals and QER Filter

Rahul Srivastava
 

Hi!,

I have been scratch building a uBitx and had been experimenting with the 12 MHz QER filter. I have noted few things and adopted some from various postings on group.

1) With the set of xtals that I have with 100pF caps and 200Z I/O filter BW is around 1.85Khz for HC49S xtals and 3.3Khz for HC49U xtals. 
    With filter based on HC49U xtals lower BW is achieved using 150pF caps but impedance drops down to 150-160 ohms. Lowering the
    BW also de grades the shape factor to around 1:2. This can be well understood considering that HC49U xtals have a lower motional inductance Lm.
2) As suggested by Alsion 82pF is working just fine in the filter. With BW of around 2.2Khz. Capacitor value is bit touchy between 82 to 100pf.
3) Q of capacitors used has a major impact on filter response. Parallelling 2 values to arrive at desired value results in a better response.

I am attaching sweeps of few different combination's on my SNA.

I would love to hear from others regarding their experience in this regard.

73

Rahul VU3WJM  

Re: ubitx CW straight key wiring

Mike Woods
 

dkuk

I want to thank you for pointing out this error on ubitx.net.   I have  fixed this temporarily by removing both the photos from that page and by deleting the reference to the hfsignals.com wire up error (now out of date)

The original wiring diagram and circuit diagram on hfsignals.com were in error.  The error in the circuit diagram was subsequently drawn to list members attention, and I updated the circuit diagram on ubitx.net accordingly.   HF Signals subsequently fixed their circuit diagram and I purged a number of references to the wire up and circuit diagram instructions error.  Obviously I missed one!

It is regrettable that you (and perhaps others?)  have taken the photo as the guide to wiring up their manual key in this manner, and come to grief with the ubitx going directly into TX mode. For that I can but apologise.  Unfortunately this problem wasn't commented on earlier.

Maintaining ubitx.net is a bit of an undertaking. The guide will, from time to time, become a bit out of date, because there is a very active community of hackers. However, I certainly don't want folk burning through finals or getting a really bad steer.   So if anybody spots an error, I attend to these as soon as they are drawn to my attention.   It's normally best to write direct to info@... for the fastest response.

73
Mike ZL1AXG ubitx.net
 


On 2/08/18 1:29 PM, dkuk@... wrote:
I've gone through 2 rounds of blowing finals before I finally found it mentioned that the wiring in the manual for the CW straight key was wrong.
It is also wrong on the website https://ubitx.net/wiring-up-a-paddle-and-straight-key/........
The resistor and blue wire must be wired to the upper right terminal in both pictures for it to work properly.
With the wiring as pictured my keyers essentially shorted the ring to the sleeve, hard keying the rig.

I would set up my keyer - plug it into the jack on the ubitx, then power the ubitx up,
unaware that as soon as I powered up, the ubitx was keyed until the finals finally fried.

This is the reference from the same web page mentioning the error in the schematic:
"There is an error on the circuit diagram and the wire up instructions for the CW Key.  The
diagrams show the key connected to pin 2 of the key jack. Pin 2 is the RING terminal, not the TIP."

Just wanted to put this out there in case anyone else is going through similar frustration.
I was so frustrated that I was ready to scrap my ubitx.


--
Mike Woods
mhwoods@...

Re: End Fed antennas w/ uBITX #ubitx

Jerry Gaffke
 

I did that back-to-back test of two myantennas.com matchboxes.
I'd say they are plenty efficient for my purposes from 3.5 to 30 mhz.

My 2 year old matchbox is referred to here as xfmrA.
Text on the box says EFHW-8010, should be exactly like the one reviewed in the March 2016 issue of QST.
I popped this one open long ago.
It's pretty much as described on that facebook page where they are trying to build clones.
    https://www.facebook.com/groups/EndFedHalfWaveAntennas/
Got two stacked toroids, each has an OD of 2.43", ID of 1.40", height of about 0.5" each.
Has 14 turns of enamel copper wire 0.072" diameter, doubled up on the first two turns
for the primary 50 ohm connection.  A couple caps in series across the 50 ohm port,
the facebook page seems to think the series combination is 100pf.
The SO239 port and the grounding post are adjacent at the bottom, have their 
grounding tabs soldered together for a short and hefty connection.  
That mechanical support eyebolt at the top has no internal electrical connection.
Facebook page thinks the toroids are Mouser PN 623-5943003801,
which is at least the right size, no idea if that's the right material.
But before trying to roll your own, look over that facebook page.
Apparently not as trivial as you might think to hit multiple bands like this.

Also borrowed a newer matchbox, about 2 months old, label says MEF-330-1K.
This was bought as a separate matchbox, not part of an antenna system.
I believe the only significant difference between the two is a vent to the atmosphere
on the side of this new one, not present on the old one.
Referred to below as xfmrB

Here's the raw data:

          -----2500-ohms-----     ----50ohm-load-----------------
           xfmrA       xfmrB       ohms-in       vout-for-50v-vin
 3.80mhz   45.6+j3.2   45.4+j5.9   38.3+j11.5    48v 
 7.20mhz   41.7-j5.5   45.3-j4.3   37.4+j1.6     52v 
14.25mhz   31.8-j3.9   33.5-j4.3   31.8+j4.7     60v 
21.35mhz   33.6+j6.9   35.4+j6.4   42.3+j12.7    48v 
29.00mhz   67.0+j12.9  65.3+j14.0  63.0+j1.5     38v 


First column shows input impedance of xfmrA when output has 2500 ohms across it.
Second column shows the same for xfmrB
Third column shows impedance into the xfmrA coax port, xfmrA is hooked back to back with xfmrB
using wires of 1 or 2 inches, and xfmrB has a 50 ohm dummy load on the coax port.
Fourth column shows peak voltage across the dummy load of the above back to back arrangement
when xfmrA is driven with 50v peak of RF.

Impedances were measured using the AQRP Vector Impedance Analyzer from Kees.

The voltage measurements were made with a Rigol DS1052E using a single 10x probe.
The probe was first used to scale the RF source for 50v at the input port,
then the probe was moved to measure the voltage across the dummy load.
I don't have a lot of faith in this Rigol, but should be fine for such relative measurements. 

I chose a 2500 ohm load for the matchboxes when measuring their impedance,
as this should give close to a 50 ohm input impedance given the 1:7 turns ratio of the toroids.
The measured impedance was somewhat less in all cases except 30mhz.
So for some reason the transformer seems to exhibit an impedance ratio in excess of 1:49
at most frequencies, and thus gives a good match for an end fed halfwave which typically
has an impedance somewhat greater than 2500 ohms. 

Given that the input impedance was mostly lower than the 50 ohm load impedance 
in that last column, it's not too surprising that the output voltage sometimes exceeded
the input voltage.   But there are some weird anomalies in those figures I haven't quite 
figured out, and I'm not totally convinced my measurements are accurate.

At all frequencies, the dummy load got plenty hot.  
The toroids of the box I had taken the lid off of did not.


#################################
A few more general notes, not part of the measurements presented here.

I've measured SWR into my EFHW antenna system, my figures agreed with 
the QST article and with the charts on the myantennas.com website.
I believe the charts on myantennas.com were created with 100' of RG8X coax
from matchbox to the SWR meter plus RF source.
My SWR measurements with a very short coax showed higher SWR figures out-of band,
but the SWR was perfectly fine within the bounds of most bands  (not all of 80m or 10m).

The SWR minimum is pretty well centered on a usable part of each band, 
due in part to the small airwound coil in the wire near where it enters the matchbox.
A possible exception is 80m, the SWR min is centered on the CW portion of the band,
a tuner of some sort would be needed to use it at 4.0 mhz.

Given that an RF source can pump power into this antenna system without
anything getting hot, I can only conclude that most of that power is properly radiated.

In what pattern it gets radiated is debatable.
Here's an FAQ for this antenna system:  https://myantennas.com/wp/f-a-q/efhw-antennas-f-a-q/
Near the bottom are four links, clicking on the first we see plots for a straight half wavelength of wire 
at 40 foot above the ground.     http://www.qsl.net/kk4obi/EFHW%20Straight.html
 
Ideally, an 80m antenna would be a half wavelength above the ground for an optimal pattern,
so 40 meters, or 130 feet.  I'd bet most hams with an 80m antenna aren't climbing trees
and rooftops much higher than the 40 foot of the plots shown in that last link.
At 40 foot, the 80m plot shows it's going pretty much straight up, a good NVIS antenna perhaps.
The others all show lobes that look to me as if they could do some good for DX.
For any ham who plans to use 80m, this EFHW is nearly equivalent to a dipole at the same height.
The other bands are gravy, and that gravy doesn't look bad.

Yes, having several different antennas would be better.
A 30 mhz rotatable beam is easy enough, and would work much better than this wire.
But for some of us, it's just a hobby.

Jerry, KE7ER
 
 

Re: 12MHz xtals and QER Filter

Ashhar Farhan
 

wow, rahul.
meticulous work! i will try this out soon.

- f

On Fri, Aug 3, 2018 at 10:47 AM, Rahul Srivastava via Groups.Io <vu3wjm@...> wrote:
Hi!,

I have been scratch building a uBitx and had been experimenting with the 12 MHz QER filter. I have noted few things and adopted some from various postings on group.

1) With the set of xtals that I have with 100pF caps and 200Z I/O filter BW is around 1.85Khz for HC49S xtals and 3.3Khz for HC49U xtals. 
    With filter based on HC49U xtals lower BW is achieved using 150pF caps but impedance drops down to 150-160 ohms. Lowering the
    BW also de grades the shape factor to around 1:2. This can be well understood considering that HC49U xtals have a lower motional inductance Lm.
2) As suggested by Alsion 82pF is working just fine in the filter. With BW of around 2.2Khz. Capacitor value is bit touchy between 82 to 100pf.
3) Q of capacitors used has a major impact on filter response. Parallelling 2 values to arrive at desired value results in a better response.

I am attaching sweeps of few different combination's on my SNA.

I would love to hear from others regarding their experience in this regard.

73

Rahul VU3WJM  


Re: End Fed antennas w/ uBITX #ubitx

Gordon Gibby
 

Thanks, Jerry!!!!!
The “heat” measurements are very much appreciated!!!!!

I’m going to send this to the folks in our area

Gordon




On Aug 3, 2018, at 01:33, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

I did that back-to-back test of two myantennas.com matchboxes.
I'd say they are plenty efficient for my purposes from 3.5 to 30 mhz.

My 2 year old matchbox is referred to here as xfmrA.
Text on the box says EFHW-8010, should be exactly like the one reviewed in the March 2016 issue of QST.
I popped this one open long ago.
It's pretty much as described on that facebook page where they are trying to build clones.
    https://www.facebook.com/groups/EndFedHalfWaveAntennas/
Got two stacked toroids, each has an OD of 2.43", ID of 1.40", height of about 0.5" each.
Has 14 turns of enamel copper wire 0.072" diameter, doubled up on the first two turns
for the primary 50 ohm connection.  A couple caps in series across the 50 ohm port,
the facebook page seems to think the series combination is 100pf.
The SO239 port and the grounding post are adjacent at the bottom, have their 
grounding tabs soldered together for a short and hefty connection.  
That mechanical support eyebolt at the top has no internal electrical connection.
Facebook page thinks the toroids are Mouser PN 623-5943003801,
which is at least the right size, no idea if that's the right material.
But before trying to roll your own, look over that facebook page.
Apparently not as trivial as you might think to hit multiple bands like this.

Also borrowed a newer matchbox, about 2 months old, label says MEF-330-1K.
This was bought as a separate matchbox, not part of an antenna system.
I believe the only significant difference between the two is a vent to the atmosphere
on the side of this new one, not present on the old one.
Referred to below as xfmrB

Here's the raw data:

          -----2500-ohms-----     ----50ohm-load-----------------
           xfmrA       xfmrB       ohms-in       vout-for-50v-vin
 3.80mhz   45.6+j3.2   45.4+j5.9   38.3+j11.5    48v 
 7.20mhz   41.7-j5.5   45.3-j4.3   37.4+j1.6     52v 
14.25mhz   31.8-j3.9   33.5-j4.3   31.8+j4.7     60v 
21.35mhz   33.6+j6.9   35.4+j6.4   42.3+j12.7    48v 
29.00mhz   67.0+j12.9  65.3+j14.0  63.0+j1.5     38v 


First column shows input impedance of xfmrA when output has 2500 ohms across it.
Second column shows the same for xfmrB
Third column shows impedance into the xfmrA coax port, xfmrA is hooked back to back with xfmrB
using wires of 1 or 2 inches, and xfmrB has a 50 ohm dummy load on the coax port.
Fourth column shows peak voltage across the dummy load of the above back to back arrangement
when xfmrA is driven with 50v peak of RF.

Impedances were measured using the AQRP Vector Impedance Analyzer from Kees.

The voltage measurements were made with a Rigol DS1052E using a single 10x probe.
The probe was first used to scale the RF source for 50v at the input port,
then the probe was moved to measure the voltage across the dummy load.
I don't have a lot of faith in this Rigol, but should be fine for such relative measurements. 

I chose a 2500 ohm load for the matchboxes when measuring their impedance,
as this should give close to a 50 ohm input impedance given the 1:7 turns ratio of the toroids.
The measured impedance was somewhat less in all cases except 30mhz.
So for some reason the transformer seems to exhibit an impedance ratio in excess of 1:49
at most frequencies, and thus gives a good match for an end fed halfwave which typically
has an impedance somewhat greater than 2500 ohms. 

Given that the input impedance was mostly lower than the 50 ohm load impedance 
in that last column, it's not too surprising that the output voltage sometimes exceeded
the input voltage.   But there are some weird anomalies in those figures I haven't quite 
figured out, and I'm not totally convinced my measurements are accurate.

At all frequencies, the dummy load got plenty hot.  
The toroids of the box I had taken the lid off of did not.


#################################
A few more general notes, not part of the measurements presented here.

I've measured SWR into my EFHW antenna system, my figures agreed with 
the QST article and with the charts on the myantennas.com website.
I believe the charts on myantennas.com were created with 100' of RG8X coax
from matchbox to the SWR meter plus RF source.
My SWR measurements with a very short coax showed higher SWR figures out-of band,
but the SWR was perfectly fine within the bounds of most bands  (not all of 80m or 10m).

The SWR minimum is pretty well centered on a usable part of each band, 
due in part to the small airwound coil in the wire near where it enters the matchbox.
A possible exception is 80m, the SWR min is centered on the CW portion of the band,
a tuner of some sort would be needed to use it at 4.0 mhz.

Given that an RF source can pump power into this antenna system without
anything getting hot, I can only conclude that most of that power is properly radiated.

In what pattern it gets radiated is debatable.
Here's an FAQ for this antenna system:  https://myantennas.com/wp/f-a-q/efhw-antennas-f-a-q/
Near the bottom are four links, clicking on the first we see plots for a straight half wavelength of wire 
at 40 foot above the ground.     http://www.qsl.net/kk4obi/EFHW%20Straight.html
 
Ideally, an 80m antenna would be a half wavelength above the ground for an optimal pattern,
so 40 meters, or 130 feet.  I'd bet most hams with an 80m antenna aren't climbing trees
and rooftops much higher than the 40 foot of the plots shown in that last link.
At 40 foot, the 80m plot shows it's going pretty much straight up, a good NVIS antenna perhaps.
The others all show lobes that look to me as if they could do some good for DX.
For any ham who plans to use 80m, this EFHW is nearly equivalent to a dipole at the same height.
The other bands are gravy, and that gravy doesn't look bad.

Yes, having several different antennas would be better.
A 30 mhz rotatable beam is easy enough, and would work much better than this wire.
But for some of us, it's just a hobby.

Jerry, KE7ER
 
 

uBITX always in transmission

negroniwalter@...
 

Assembled immediately and fully functional. I did dozens of QSOs in Psk31 and FT8. Now it passes immediately in transmission just turned on, I tried to detach the orange wire at the entrance 5 to Raduino  without result. As soon as the device is switched on after a second bootstrap, it immediately switches to TX, the 4.7 kOhm resistor between the blue wire (2) and the green wire (3) is connected and the blue wire is disconnected from the earth.
Thanks for your help.
Iw5dtf Walter Negroni

Bi-Colour tx/rx led

Ian Reeve
 

Using the wiring as detailed in earlier articles I find that 2.0K resistor in each outer lead with the led centre pin earhed (or -ve) gived for me just the right brightness. You could try 2.2K which for me was just a touch dim. I found the resistor values as shown on the picture of the led on veroboard was too bright and so I suggest a bit of experimentation.
I have fully assembled mine now which is "stock" using the mBITX case and using the included extra pcb's everything works straight off, no issues with receive or transmit audio.A lovely QRP rig at a very keen price.

73

M0IDR

Re: Arduino v1.28 for BitX40 released #bitx40

terry hughes
 

hi
what version of the sketch is installed on the bitx40 currently on sale.

terry gm4dso

Re: End Fed antennas w/ uBITX #ubitx

Warren Allgyer
 

Jerry and Gordon

Great data Jerry! I too am scratching my head over some the entries but it is a start and good to know.

I don't understand the impedance variation of the terminated pair and the terminated transformers individually. My test did not show that and it raises a bit of a red flag. I also looked more closely at the SWR table published by the manufacturer. Having stared at similar VIA outputs in my lab I noted two things. The cyclic VSWR pattern is very likely the result of the 100 feet of coax, very close to a half wave at 80 meters, alternating between a quarter wave transformer and a half wave at harmonics of 80 meters or whatever is the actual length of the coax. Notice that these peaks are attenuated as you approach 30 MHz. That is indicative of the loss in the system at those frequencies. The lower the loss of the transformer the higher and more uniform would be these peaks.

A final note on the heat: the numbers you show indicate losses on each individual transformer between 0.2 and 0.8 dB which is significantly better than I measured using the spectrum analyzer/tracking generator. As such I would not expect much heating from the 5-8 watts of input power you used. Additionally, you were using the "2K" model which uses a double stacked transformer for additional heat dissipation capability. And this combo was terminated in a perfect resistive load. When terminated in the wire the load will be very different and highly reactive on some bands. As such the transformer losses will rise dramatically but the apparent VSWR will not due to the losses. I sure would like to see a VIA plot of the wire itself through the transformer.

Your antenna appears to accept power much better than I suspected. The strategically positioned 6 turn air wound coil has a lot to do with that because it is what allows the wire length to change electrically and let harmonically related bands fall into the integer related even harmonic. It is a puzzle to me that the antenna shows resonant characteristics on non-harmonically related bands like 30 and 15 meters. That may be the witchcraft element of the coil combined with a strategic length of coax feedline.

Thank you for doing and reporting on all of that work! Great job.

WA8TOD

Re: End Fed antennas w/ uBITX #ubitx

ajparent1/KB1GMX
 

Warren,

Notice that these peaks are attenuated as you approach 30 MHz. That is indicative of the loss in the system at those frequencies. The lower the loss of the transformer the higher and more uniform would be these peaks.

While the transformer may contribute along with coax losses bare wire testing also shows that.  By that I mean the wire
itself shows a progressing reduction in the peaks.  This is due to radiation, even though the mismatch may be there some
amount of RF is always radiated and the returned energy is not there as a result.  An infinitely (or very long)  long wire at
some high frequency exhibits a very low return loss with increasing frequency.  However in the real world this can be
seen with a 20M wire at VHF. 

I can detail why that happens but resistance of the wire is not constant due to skin effect and very long wires at very
high frequencies are very low Q as a result.

Allison

Re: 12MHz xtals and QER Filter

ajparent1/KB1GMX
 

If the sweep rate is too fast the filter will exhibit tilt.

Also when I went t 82PF I used ATC 100B 5% parts I had so the result was less random.
I also found that the terminating impedance was better and the filter ripple was better with a
differently constructed transformer (ft43-2402 2 hole cores).  I would later design a 100 ohm
transformer that gave better results (2.7khz and flatter).

Keep in mind we have no data across more than a small sample of crystals and maybe only
one vendor.  So variation is expected.

Allison

Re: Arduino v1.28 for BitX40 released #bitx40

Allard PE1NWL
 

As far as I know the stock firmware for BitX40 is still Asshar's initial version v1.01
You can still download it from https://github.com/afarhan/bitx40

73 Allard PE1NWL

Re: End Fed antennas w/ uBITX #ubitx

Jerry Gaffke
 

Warren,

My dummy load is twenty 1k metal film resistors of 3 Watts.  So 50 ohms at 60 Watts.
With around 50 volts peak going in (100 volts peak-to-peak), that's on the order of  50*0.707 * (50*0.707) / 50 = 25 Watts of RF.
At times I cranked the RF up to 100 Watts.  The toroids are admittedly more massive than the resistors, but no discernible heating
in the toroids does give a little added confidence to the conclusion that we are not burning much power there.

> The cyclic VSWR pattern is very likely the result of the 100 feet of coax

As I've said earlier, when I measure my antenna system with just a few feet of coax between the matchbox and the vector impedance analyzer,
I get the same peaks and valleys in the VSWR as shown on the website but the peaks are more pronounced.   
The peaks and valleys are due to resonance in the wire, not something about the coax.  
Adding coax primarily affects frequencies at which the matchbox has a high VSWR, when losses in the coax become significant.
On a positive note, the coax does lower the VSWR at somewhat off resonant frequencies, allowing use there without a tuner.
Most non-WARC bands are usable across the entire band without a tuner even with a short coax, 80m and 10m are the primary exceptions

> It is a puzzle to me that the antenna shows resonant characteristics on non-harmonically related bands like 30 and 15 meters.

30m is near the third harmonic of 80m:  3.6*3 = 10.8mhz       Though far enough away that you still want to use a tuner with this antenna
21mhz is near the 6'th harmonic of 80m:   3.6*6 = 21.6mhz    That one's usable without a tuner.

> Additionally, you were using the "2K" model 

These are both rated at "1kW ICAS".   Danny (and his competition) does offer 2kW transformers, I have no idea what's inside them.
I have nothing here capable of more than 100W, reports are that at 1kW the toroids do heat up badly if you hold the key down too long.
Since the box is sealed and up on the roof somewhere, your primary indication is that the SWR starts rising.
On bands such as 30m where the wire is not quite resonant, you definitely don't want to go more than a few hundred Watts.


>  And this combo was terminated in a perfect resistive load. When terminated in the wire the load will be very different
>  and highly reactive on some bands. As such the transformer losses will rise dramatically but the apparent VSWR
>  will not due to the losses. I sure would like to see a VIA plot of the wire itself through the transformer.

At any integer multiple of the fundamental, the wire is resonant and purely resistive.
I'd guess that this is closer to 3000 ohms than 2500 ohms.
At resonance the measured SWR of the antenna system when using just a few feet of coax
is down at 1.2 or less, suggesting negligible losses.  (See the published charts).
Losses do rise when somewhat off resonance, as is the case with 30m.

Jerry, KE7ER


On Fri, Aug 3, 2018 at 04:46 AM, Warren Allgyer wrote:

Jerry and Gordon

Great data Jerry! I too am scratching my head over some the entries but it is a start and good to know.

I don't understand the impedance variation of the terminated pair and the terminated transformers individually. My test did not show that and it raises a bit of a red flag. I also looked more closely at the SWR table published by the manufacturer. Having stared at similar VIA outputs in my lab I noted two things. The cyclic VSWR pattern is very likely the result of the 100 feet of coax, very close to a half wave at 80 meters, alternating between a quarter wave transformer and a half wave at harmonics of 80 meters or whatever is the actual length of the coax. Notice that these peaks are attenuated as you approach 30 MHz. That is indicative of the loss in the system at those frequencies. The lower the loss of the transformer the higher and more uniform would be these peaks.

A final note on the heat: the numbers you show indicate losses on each individual transformer between 0.2 and 0.8 dB which is significantly better than I measured using the spectrum analyzer/tracking generator. As such I would not expect much heating from the 5-8 watts of input power you used. Additionally, you were using the "2K" model which uses a double stacked transformer for additional heat dissipation capability. And this combo was terminated in a perfect resistive load. When terminated in the wire the load will be very different and highly reactive on some bands. As such the transformer losses will rise dramatically but the apparent VSWR will not due to the losses. I sure would like to see a VIA plot of the wire itself through the transformer.

Your antenna appears to accept power much better than I suspected. The strategically positioned 6 turn air wound coil has a lot to do with that because it is what allows the wire length to change electrically and let harmonically related bands fall into the integer related even harmonic. It is a puzzle to me that the antenna shows resonant characteristics on non-harmonically related bands like 30 and 15 meters. That may be the witchcraft element of the coil combined with a strategic length of coax feedline.

Thank you for doing and reporting on all of that work! Great job.

WA8TOD

Re: End Fed antennas w/ uBITX #ubitx

Jack Purdum
 

Jerry:

We did the same thing:

Inline image

but then put it in a quart can filled with mineral oil. It will take 250W for 5 minutes without damage to the components. (However, you could probably cook French Fries in the oil.) We added a simple display to give an idea of the power going into it:

Inline image

Jack, W8TEE

On Friday, August 3, 2018, 10:24:01 AM EDT, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:


Warren,

My dummy load is twenty 1k metal film resistors of 3 Watts.  So 50 ohms at 60 Watts.
With around 50 volts peak going in (100 volts peak-to-peak), that's on the order of  50*0.707 * (50*0.707) / 50 = 25 Watts of RF.
At times I cranked the RF up to 100 Watts.  The toroids are admittedly more massive than the resistors, but no discernible heating
in the toroids does give a little added confidence to the conclusion that we are not burning much power there.

> The cyclic VSWR pattern is very likely the result of the 100 feet of coax

As I've said earlier, when I measure my antenna system with just a few feet of coax between the matchbox and the vector impedance analyzer,
I get the same peaks and valleys in the VSWR as shown on the website but the peaks are more pronounced.   
The peaks and valleys are due to resonance in the wire, not something about the coax.  
Adding coax primarily affects frequencies at which the matchbox has a high VSWR, when losses in the coax become significant.
On a positive note, the coax does lower the VSWR at somewhat off resonant frequencies, allowing use there without a tuner.
Most non-WARC bands are usable across the entire band without a tuner even with a short coax, 80m and 10m are the primary exceptions

> It is a puzzle to me that the antenna shows resonant characteristics on non-harmonically related bands like 30 and 15 meters.

30m is near the third harmonic of 80m:  3.6*3 = 10.8mhz       Though far enough away that you still want to use a tuner with this antenna
21mhz is near the 6'th harmonic of 80m:   3.6*6 = 21.6mhz    That one's usable without a tuner.

> Additionally, you were using the "2K" model 

These are both rated at "1kW ICAS".   Danny (and his competition) does offer 2kW transformers, I have no idea what's inside them.
I have nothing here capable of more than 100W, reports are that at 1kW the toroids do heat up badly if you hold the key down too long.
Since the box is sealed and up on the roof somewhere, your primary indication is that the SWR starts rising.
On bands such as 30m where the wire is not quite resonant, you definitely don't want to go more than a few hundred Watts.


>  And this combo was terminated in a perfect resistive load. When terminated in the wire the load will be very different
>  and highly reactive on some bands. As such the transformer losses will rise dramatically but the apparent VSWR
>  will not due to the losses. I sure would like to see a VIA plot of the wire itself through the transformer.

At any integer multiple of the fundamental, the wire is resonant and purely resistive.
I'd guess that this is closer to 3000 ohms than 2500 ohms.
At resonance the measured SWR of the antenna system when using just a few feet of coax
is down at 1.2 or less, suggesting negligible losses.  (See the published charts).
Losses do rise when somewhat off resonance, as is the case with 30m.

Jerry, KE7ER


On Fri, Aug 3, 2018 at 04:46 AM, Warren Allgyer wrote:

Jerry and Gordon

Great data Jerry! I too am scratching my head over some the entries but it is a start and good to know.

I don't understand the impedance variation of the terminated pair and the terminated transformers individually. My test did not show that and it raises a bit of a red flag. I also looked more closely at the SWR table published by the manufacturer. Having stared at similar VIA outputs in my lab I noted two things. The cyclic VSWR pattern is very likely the result of the 100 feet of coax, very close to a half wave at 80 meters, alternating between a quarter wave transformer and a half wave at harmonics of 80 meters or whatever is the actual length of the coax. Notice that these peaks are attenuated as you approach 30 MHz. That is indicative of the loss in the system at those frequencies. The lower the loss of the transformer the higher and more uniform would be these peaks.

A final note on the heat: the numbers you show indicate losses on each individual transformer between 0.2 and 0.8 dB which is significantly better than I measured using the spectrum analyzer/tracking generator. As such I would not expect much heating from the 5-8 watts of input power you used. Additionally, you were using the "2K" model which uses a double stacked transformer for additional heat dissipation capability. And this combo was terminated in a perfect resistive load. When terminated in the wire the load will be very different and highly reactive on some bands. As such the transformer losses will rise dramatically but the apparent VSWR will not due to the losses. I sure would like to see a VIA plot of the wire itself through the transformer.

Your antenna appears to accept power much better than I suspected. The strategically positioned 6 turn air wound coil has a lot to do with that because it is what allows the wire length to change electrically and let harmonically related bands fall into the integer related even harmonic. It is a puzzle to me that the antenna shows resonant characteristics on non-harmonically related bands like 30 and 15 meters. That may be the witchcraft element of the coil combined with a strategic length of coax feedline.

Thank you for doing and reporting on all of that work! Great job.

WA8TOD

Re: End Fed antennas w/ uBITX #ubitx

Gordon Gibby
 

Jerry --- likely that a simulator would tell you how much and how quickly reactive components add in as you move away from the exact resonant frequency.   It does seem that significant reactive components might increase losses, huh?  (I'm not an expert on that).


Any information on how far from resonant you can be before reactance increases signficnat in an end-fed, high impedance antenna, and then next, how that changes toroid losses????   that might be the $64 question.



On my homebrew off-center-fed balun diplose they "appear" more broadbanded......suggesting that the closer you get to the end, the less the importance of small variations from exact resonant frequency?


cheers,


gordon




From: BITX20@groups.io <BITX20@groups.io> on behalf of Jerry Gaffke via Groups.Io <jgaffke@...>
Sent: Friday, August 3, 2018 10:23 AM
To: BITX20@groups.io
Subject: Re: [BITX20] End Fed antennas w/ uBITX
 
Warren,

My dummy load is twenty 1k metal film resistors of 3 Watts.  So 50 ohms at 60 Watts.
With around 50 volts peak going in (100 volts peak-to-peak), that's on the order of  50*0.707 * (50*0.707) / 50 = 25 Watts of RF.
At times I cranked the RF up to 100 Watts.  The toroids are admittedly more massive than the resistors, but no discernible heating
in the toroids does give a little added confidence to the conclusion that we are not burning much power there.

> The cyclic VSWR pattern is very likely the result of the 100 feet of coax

As I've said earlier, when I measure my antenna system with just a few feet of coax between the matchbox and the vector impedance analyzer,
I get the same peaks and valleys in the VSWR as shown on the website but the peaks are more pronounced.   
The peaks and valleys are due to resonance in the wire, not something about the coax.  
Adding coax primarily affects frequencies at which the matchbox has a high VSWR, when losses in the coax become significant.
On a positive note, the coax does lower the VSWR at somewhat off resonant frequencies, allowing use there without a tuner.
Most non-WARC bands are usable across the entire band without a tuner even with a short coax, 80m and 10m are the primary exceptions

> It is a puzzle to me that the antenna shows resonant characteristics on non-harmonically related bands like 30 and 15 meters.

30m is near the third harmonic of 80m:  3.6*3 = 10.8mhz       Though far enough away that you still want to use a tuner with this antenna
21mhz is near the 6'th harmonic of 80m:   3.6*6 = 21.6mhz    That one's usable without a tuner.

> Additionally, you were using the "2K" model 

These are both rated at "1kW ICAS".   Danny (and his competition) does offer 2kW transformers, I have no idea what's inside them.
I have nothing here capable of more than 100W, reports are that at 1kW the toroids do heat up badly if you hold the key down too long.
Since the box is sealed and up on the roof somewhere, your primary indication is that the SWR starts rising.
On bands such as 30m where the wire is not quite resonant, you definitely don't want to go more than a few hundred Watts.


>  And this combo was terminated in a perfect resistive load. When terminated in the wire the load will be very different
>  and highly reactive on some bands. As such the transformer losses will rise dramatically but the apparent VSWR
>  will not due to the losses. I sure would like to see a VIA plot of the wire itself through the transformer.

At any integer multiple of the fundamental, the wire is resonant and purely resistive.
I'd guess that this is closer to 3000 ohms than 2500 ohms.
At resonance the measured SWR of the antenna system when using just a few feet of coax
is down at 1.2 or less, suggesting negligible losses.  (See the published charts).
Losses do rise when somewhat off resonance, as is the case with 30m.

Jerry, KE7ER


On Fri, Aug 3, 2018 at 04:46 AM, Warren Allgyer wrote:

Jerry and Gordon

Great data Jerry! I too am scratching my head over some the entries but it is a start and good to know.

I don't understand the impedance variation of the terminated pair and the terminated transformers individually. My test did not show that and it raises a bit of a red flag. I also looked more closely at the SWR table published by the manufacturer. Having stared at similar VIA outputs in my lab I noted two things. The cyclic VSWR pattern is very likely the result of the 100 feet of coax, very close to a half wave at 80 meters, alternating between a quarter wave transformer and a half wave at harmonics of 80 meters or whatever is the actual length of the coax. Notice that these peaks are attenuated as you approach 30 MHz. That is indicative of the loss in the system at those frequencies. The lower the loss of the transformer the higher and more uniform would be these peaks.

A final note on the heat: the numbers you show indicate losses on each individual transformer between 0.2 and 0.8 dB which is significantly better than I measured using the spectrum analyzer/tracking generator. As such I would not expect much heating from the 5-8 watts of input power you used. Additionally, you were using the "2K" model which uses a double stacked transformer for additional heat dissipation capability. And this combo was terminated in a perfect resistive load. When terminated in the wire the load will be very different and highly reactive on some bands. As such the transformer losses will rise dramatically but the apparent VSWR will not due to the losses. I sure would like to see a VIA plot of the wire itself through the transformer.

Your antenna appears to accept power much better than I suspected. The strategically positioned 6 turn air wound coil has a lot to do with that because it is what allows the wire length to change electrically and let harmonically related bands fall into the integer related even harmonic. It is a puzzle to me that the antenna shows resonant characteristics on non-harmonically related bands like 30 and 15 meters. That may be the witchcraft element of the coil combined with a strategic length of coax feedline.

Thank you for doing and reporting on all of that work! Great job.

WA8TOD

Re: Arduino v1.28 for BitX40 released #bitx40

Praba Karan
 

Stock firmware support cat control ?
Just I want to know.


On Fri, Aug 3, 2018, 7:32 PM Allard PE1NWL <pe1nwl@...> wrote:
As far as I know the stock firmware for BitX40 is still Asshar's initial version v1.01
You can still download it from https://github.com/afarhan/bitx40

73 Allard PE1NWL

Re: Arduino v1.28 for BitX40 released #bitx40

Jack Purdum
 

There's a file named ubitx_cat.ino, so I'm guessing yes. A good way to find out is to download the code and look at it.

Jack, W8TEE

On Friday, August 3, 2018, 10:52:49 AM EDT, Praba Karan <vu3dxr@...> wrote:


Stock firmware support cat control ?
Just I want to know.


On Fri, Aug 3, 2018, 7:32 PM Allard PE1NWL <pe1nwl@...> wrote:
As far as I know the stock firmware for BitX40 is still Asshar's initial version v1.01
You can still download it from https://github.com/afarhan/bitx40

73 Allard PE1NWL

Re: End Fed antennas w/ uBITX #ubitx

Jerry Gaffke
 

Jack,

It's not an accident that mine is similar.
Thanks for the pointer to the cheap metal film 3W resistors a few months ago!
Mine's much uglier, just twisted the ends together, though kept the
resistors spaced far enough to allow some airflow.
In your case, that's french-fry oil-flow.

I'm using 20 of this 1k 3W part from Mouser at $0.10 each
    283-1.0K-RC
Four of the 200 ohm 3W part in parallel would be plenty as a dummy load for the uBitx:
    283-200-RC

If somebody were to kit them up for the group along with a schottky diode RF probe,
the surface mount resistors might be easier to mail.

Jerry 

 
    


On Fri, Aug 3, 2018 at 07:30 AM, Jack Purdum wrote:
We did the same thing:
 

Re: End Fed antennas w/ uBITX #ubitx

Jerry Gaffke
 

Gordon,

I think just measuring the SWR into the antenna system using a short 5 to 10 foot of coax from matchbox to antenna analyzer 
gives a pretty good indication of where things will start getting lossy, for both loss in the toroid and in a long coax.
The published SWR charts on myantennas.com (and QST review) are a good indication of what you will get,
agree well for frequencies at which the SWR is under 2.0.  With a long piece of coax, the low SWR numbers
remain about the same, the high SWR numbers shoot up considerably. 
That's as I recall, it's been a couple years since I looked hard at that.

You do need some coax between antenna analyzer and the matchbox.
Take it down to a few inches with an electrically isolated analyzer and things get whacky
due to lack of counterpoise.

Jerry, KE7ER


On Fri, Aug 3, 2018 at 07:33 AM, Gordon Gibby wrote:

Jerry --- likely that a simulator would tell you how much and how quickly reactive components add in as you move away from the exact resonant frequency.   It does seem that significant reactive components might increase losses, huh?  (I'm not an expert on that).

 

Any information on how far from resonant you can be before reactance increases signficnat in an end-fed, high impedance antenna, and then next, how that changes toroid losses????   that might be the $64 question.

 

 

On my homebrew off-center-fed balun diplose they "appear" more broadbanded......suggesting that the closer you get to the end, the less the importance of small variations from exact resonant frequency?

 

cheers,

 

gordon

 

Re: experience with Sunil VU3SUA's enclosures #ubitx

Dave New
 

I found the headphone jack on the front panel PCB only had audio going to the left channel in my stereo headset.  I pulled everything apart, and discovered that there was no PCB trace going to the right channel pin on the headphone jack. I soldered a jumper from a cut-off wire across the left and right channel pins, and put everything back together.

The headphone works fine, now, both channels, and it still disconnects the internal speaker, as expected.

73,

-- Dave, N8SBE

-------- Original Message --------
Subject: Re: [BITX20] experience with Sunil VU3SUA's enclosures #ubitx
From: "Philip" <philip.g7jur@...>
Date: Thu, August 02, 2018 6:16 pm
To: BITX20@groups.io

Yes same problem here.

Philip.