Date   

Re: Low Pass Filer Board Timing. #bpf #wspr #u3s

geoff M0ORE
 

If you have a double beam scope, put chan 1 (DC ) on the line activating the relay and chan 2 (AC) on the output somewhere. You can then measure the time lag. Another way would be to put chan 1 ( now AC ) on the RF input to the relay and chan 2 as before.

We wait to hear your results.

On 09/09/2020 08:02, Phil Crockford wrote:

Does anyone have a definitive answer to the following: -

What is the time delay between the activation of a selected low pass filter, via B0-B5 from the U3S board, and the start of a WSPA transmission?

Thanks

 

Phi G8IOA


Re: Thoughts on Low Power and fewer turns on LP filter toroids

Brian George
 

Thank you Hans and also Shirley for your helpful replies. All understood and noted.

73
Brian
G3ZOH

ps - Hans - hope you and your family are keeping well. 


Filter select timing. #wspr #u3s

Phil Crockford
 

Can anyone give me a definitive answer to the following: -

What is the timing of the Filter Output control lines B0 to B5 and the start of the current WSPA transmission?

One assumes that the appropriate Filter select line is set and then the transmission starts.

 

How long after the Filter line B0 to B5 are activated does the transmission start?

 

Thanks Phil G8IOA


Re: Thoughts on Low Power and fewer turns on LP filter toroids

Hans Summers
 

Hi Brian
 
Just a passing thought ...if component tolerances are a key factor contributing to low output when using the 20m and 30m LPFs then why aren't about 50% of constructors having to ADD turns and why is it only on 20m and 30m? I had exactly the same issue but a VNA scan showed that the 3dB cut-off points were ideal for both 20m and 30m - about 11% above the highest operating frequency. What I did discover was that the insertion loss was a little higher on the 20m LPF and the passband on the 30m LPF sloped down towards the cut-off pojnt instead of being flat. 

The number of turns specified in the manual tends to be a bit on the high side. Why? Because it is the theoretically calculated number of turns. But the theory assumes an evenly spaced turn distribution around the core which in practice is not achieved, due to several factors including there is always a gap between the ends of the windings, and that perfectly evenly spacing is impossible. Furthermore there are variations in winding styles, some people wind the wire very tight against the toroid former and for others, more loose windings leave a bit of an air gap between the toroid and the wire. 

I am quite happy with the turns specification in the manual being a bit on the high side. Why? Well, have you ever tried adding a turn to a toroid? It's certainly a lot easier to remove them :-) 

Another point is that a straightforward plot of the characteristics of the LPF on a VNA or spectrum analyzer is not the whole story either. This is because the BS170's end of the LPF has to be matched to the impedance of the PA. Since capacitor C30, the three BS170s, and L4 (all these are elements of the Class-E resonant drain load circuit) are also variable due to component tolerances/winding styles, the impedance match is an additional factor. In my opinion you just have to play with it. 

As an example. Here I am testing and aligning some QCX+ kits today which have been built here at QRP Labs, for selling as Assembled radios. Most are for 40m and are generally easier. But I have one on the bench right now which is a 30m unit. Initially the Vpp on the 'scope was 24V which is just 1.4W of output power with 12.0V supply. 

Time to play! 

I removed two turns from L3 and spread the turns out - I find L3 often needs a turn or two removed, it is the inductor closest to the PA and I think getting this impedance matched better is a good first step. Then I bunched up L2 and L1 a bit. In the end I now read 4.6W with 12.0V supply, increasing to 6.2W with 13.8V supply. From 1.4W to 4.6W all just by altering the inductances of L1/L2/L3. Remember removing turns is not always the answer - in this case, two turns removed from L3 reduces the inductance; but L1 and L2 I just squeezed the turns (none removed) which increases the inductance. 

73 Hans G0UPL
http://qrp-labs.com


Re: Thoughts on Low Power and fewer turns on LP filter toroids

Shirley Dulcey KE1L
 

If the inductor values are low on a low pass filter, which is why you might want to add turns, it will cause the cutoff frequency to be higher than it was designed to be. You won't detect that issue by seeing low power output. It will cause the radio's harmonic suppression to be reduced but you'll need a spectrum analyzer to find that, and the radio will probably still meet the standards for spurious emissions. It could also change the response curve a bit, but again you won't detect that without equipment to measure the filter response. (I'd probably look for that by attaching a noise generator to the input, probing the receiver just after the low pass filter, and feeding that signal into either a spectrum analyzer or a wideband SDR. That would show the filter cutoff and shape, including any passband ripple.

If loading the circuit at that point turns out to be a problem, an alternate place to test would be immediately after one of the receive preamps -- on a QCX+ that's either JP7 or JP8. That has the downside of also bringing in the shape of the bandpass filter that is one of the functions of T1 and its neighboring components.


On Wed, Sep 9, 2020 at 5:21 AM Brian George via groups.io <george.familyuk=ntlworld.com@groups.io> wrote:
Just a passing thought ...if component tolerances are a key factor contributing to low output when using the 20m and 30m LPFs then why aren't about 50% of constructors having to ADD turns and why is it only on 20m and 30m? I had exactly the same issue but a VNA scan showed that the 3dB cut-off points were ideal for both 20m and 30m - about 11% above the highest operating frequency. What I did discover was that the insertion loss was a little higher on the 20m LPF and the passband on the 30m LPF sloped down towards the cut-off pojnt instead of being flat. 

73
Brian
G3ZOH  


Re: Thoughts on Low Power and fewer turns on LP filter toroids

Brian George
 

Just a passing thought ...if component tolerances are a key factor contributing to low output when using the 20m and 30m LPFs then why aren't about 50% of constructors having to ADD turns and why is it only on 20m and 30m? I had exactly the same issue but a VNA scan showed that the 3dB cut-off points were ideal for both 20m and 30m - about 11% above the highest operating frequency. What I did discover was that the insertion loss was a little higher on the 20m LPF and the passband on the 30m LPF sloped down towards the cut-off pojnt instead of being flat. 

73
Brian
G3ZOH  


Low Pass Filer Board Timing. #bpf #wspr #u3s

Phil Crockford
 

Does anyone have a definitive answer to the following: -

What is the time delay between the activation of a selected low pass filter, via B0-B5 from the U3S board, and the start of a WSPA transmission?

Thanks

 

Phi G8IOA


Re: U3S Output #u3s

Phil Crockford
 

Yes I have done it. It involves a board with relays driven from the B0 - B5 outputs on the U3S board. Each relay controls the amount of Bias on the PA transistor via a potentiometer, one for each of the outputs.
It works well. If you want diagram and notes let me know.

No doubt there are other ways of doing it but this was done with what i has in my box.

Phil G8IOA


QRP labs Arduino Shield Kit Schematic #shield

KG5ZID Hardy
 

Is there a better schematic than the hand-drawn one shown in the assembly instructions? I am attempting to use this shield with an AD9850 DDS module, and the LPF kit. In particular, the AD9850_reset pin is not shown on the hand drawn schematic. Using the numbering scheme used on the schematic, this would be pin 15, next to Data pin 14 on the module header. On my shield, this pin appears to be grounded. Furthermore, the header pin which would normally connect to the Arduino Uno D12 pin also appears to be grounded. This is shown on the schematic to be connected to Band 4. I don't see any solder bridges but that's always a possibility!
--KG5ZID Hardy


Re: QRP-LABS Low Pass Filter upgrade

Timothy Fidler
 

It is possible to armour up say a 40 w PCB for a LP  filter  like the one from Far Ccts  (Also sold out of India  by Sunil Lakarami) with heavy Cu wire , solder stitched along  existinig traces.  you need to handle the bare wire with gloved hands so it does not get sweat on it so you can then spray it with Polyurethane varnish to protect the critical outer layer where RF will be travelling.  DO NOT flow solder all over the copper. you need bead welds of solder to the PCB trace every now and then. Obviously the CU is being run down the guts of the existing PCB trace.  Where you have vias in a PC B you will have to work out a solution.  Navships on Ebay sells TE insulated Cu wire 1.0 mm dia which can be a shovel out of hard place.  take care not to breath teflon fumes if soldering it.  Navships is also known as John's wire shop.  I don't believe he has any solid core wire greater than 1.0mm. TE insulated wire of any sort is a nice thing to have for this sort of duty. 

Sod's law - such a board will be sized for say type T50 toroids. If you want to move it to a HIGHER PLane you may get mechanical clashes. So a 5 filter PCB may turn into a 3 band PCB. " Ya get that on these big jobs"

regards, TE Fid


Replacement Parts for QCX+

Len W1LEN
 

I'm looking for a mail order/online source to buy small quantities of replacement parts for QCX+, specifically IC7 LM4562, and R25 3.3K ohm resistor.  Any suggestions would be much appreciated.  Thanks very much.

Len W1LEN

Virus-free. www.avg.com


Re: Thoughts on Low Power and fewer turns on LP filter toroids

Phil/K3UT
 

I’ve always kept a 50ohm dummy load on the output. I will take a look at L4 tomorrow, first by compressing and then spacing the windings.  Then i may remove a turn. More later. 

Phil K3UT 


Re: #40m qcx+ #40m

Bruce K1FFX
 

If your logging software is N1MM+, you may have better results using the "KENWOOD-SLOW" setting.

- Bruce K1FFX


Re: Select Button on Alignment QCX+ 20m

N3MNT
 

Could be a simple issue.  Make sure you did not install the know too far on the shaft ( close to the case) or it will not have sufficient travel to activate the switch.


Skeeter Hunt 2020 Results published.

Larry Makoski
 

To all Skeeters and Skeeter Hunters,

You are ALL chmapions in my book! Thank you all for participating - without you, this event is a big ZERO. You folks make it what it is. And while you're tops, special kudos go to:

Gene N5GW - 1st Place overall with 25,912 points
Kent as N0SS - 2nd Place overall with 21,316 points
Dave AB9CA - 3rd Place overall with 17. 806 points
Peter NN9K - 4th Place overall with 16,381 points
Marc W4MPS - 5th Place overall with 14.020 points

The 2020 Skeeter Scoreboard is available for viewing in its entirety at:

https://drive.google.com/file/d/18QkjuDoQik9OYXQeC19l4kUPCyAgYcQU/view?usp=sharing

The soapbox will follow ASAP as well as certificates to those who earned them.

Thanks again to all who particpated and and to those who sent in log summaries, comments and photos.

73 de Larry W2LJ - Skeeter Hunt Contest Manager - Skeeter # 13 in perpetuity.


Re: Thoughts on Low Power and fewer turns on LP filter toroids

@CurtisM
 

Phil

the 5 watt outside is specified for higher voltage than 13.8 volts.  okay a few claim more, but I trust the designer's data. 

your rigs are working wonderfully 3 watts to 5 watts is a small fraction of one S-unit !  only your power meter knows the difference. 

okay to tweak a rig when building - otherwise we may as well order it already built (funny thing, that option is coming!). 

all seems well - enjoy its radiations - wow these QCX have wonderful receivers! 

73 Curt


Re: QCX #smoked ? #smoked

@CurtisM
 

John

let's not conclude anything yet - but suffice it to say WSPR can be rough on this rig - the original QCX without any heat sinking on the bs170 finals.  I can't speak to the qcx+ on WSPR, but the heatsink at least looks nice! 

let's see - single band rig - if you do WSPR once each 10 minutes - I would think it should work if your antenna has a reasonable match.  kaput?  I would think only the bs170 finals take punishment - order a batch of them from W8DIZ if you are stateside. 

now i did smoke some bs170 in my QCX - when I plugged in GPS and did not realize it set rig into transmit.  hang in there I hope the QCX is still okay. 

73 curt


Re: DSB & AM on 222MHz with IQ receiver, can it be done? #building #vhf #si5351a #fst3253 #1.25M #fst3253 #ht #building #vhf #si5351a

freefuel@...
 

Not exactly the direction I was looking to turn, but this seems to have some merit, https://www.rtl-sdr.com/rpitx-v2-released-easily-record-and-replay-with-rtl-sdr-and-a-raspberry-pi/

-Justin N2TOH 


Re: #40m qcx+ #40m

Don Blachura
 

Tu Ron. At 83 my mind is getting a little rusty.
Tu agn.

Don...w2xb


Re: #40m qcx+ #40m

Ronald Taylor
 

 Page 138 in the manual... Kenwood TS-480


4.28 CAT Control commands (PC remote operation)

The CAT command system is intended to allow the QCX+ to be used with logging software (general and contest) which uses CAT control commands to query the transceiver for information entered into the log, typically operating frequency, mode etc. A subset of the Kenwood TS-480 command set is implemented, with a few minor modifications.



page138image28583472

QCX+ assembly Rev 1.03                                                                                                           138


On Tue, Sep 8, 2020 at 1:30 PM Don Blachura via groups.io <haircutter=verizon.net@groups.io> wrote:
Need a liitle help. What rig do you select in logging software to use the "cat' on the qcx+?
I see the port in my Device manager, but from there I am lost.

Don...w2xb
(using aclog by n3jfp)

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