Date   

Re: kd8cec sketch

Jack Zielke
 

I put in a pull request to fix this 4 days ago.  Linux uses a case-sensitive filesystem so you need to change the case.  The case is already correct in ubitx.h.  It is incorrect in softserial_tiny.cpp.  If you change that 1 letter it should compile for you (it did for me).

https://github.com/phdlee/ubitx/pull/41


Re: Harmonics measured by Warren. How bad?

ajparent1/KB1GMX <kb1gmx@...>
 

Tom,

A L network L first is a low pass.  However most are run at such low loaded
Q they are not very useful for harmonic control.  Typical Q is under 10 and
2 is not uncommon.

Allison


Re: Harmonics measured by Warren. How bad?

ajparent1/KB1GMX <kb1gmx@...>
 

Brent,

Yes, QST September 1988, bandpass filters.

For 15, 12 and 10.

Allison


Re: Harmonics measured by Warren. How bad?

Brent Seres/ VE3CUS
 

Yes, the tune able preselector idea is what I was thinking. I believe I have all the parts in my junk box. Also, has anyone here built a tap to sample signals from a dummy load? I don't have a spectrum analyzer, but thought I could use my SDR to measure with a suitable tap. I've done the math, but would be interested to hear how others have done it.


Re: kd8cec sketch

terry hughes
 

hi

works perfectly in windows but linux is proving a bit difficult

terry gm4dso


Re: End Fed antennas w/ uBITX #ubitx

iz oos
 

Referring to the parallel resonant transformer (especially the excellent description by Chuck N1KGY), if I wanted to put the capacitor on the low impedance side instead of the high side, let's say at 10Mhz which value of reactance should be on the low side? 5.5uH?


Il 27/ago/2018 12:32, "iz oos" <and2oosiz2@...> ha scritto:

Please disregard my previous post as it was a comment on another thread!


Il 27/ago/2018 09:31, "iz oos" <and2oosiz2@...> ha scritto:

Hi Chuck, indeed I was thinking with the logic of building wideband transmission line transformers which cannot be easily built with such a high transformation ratio. As far as I understand you would put the capacitor at the antenna side. If I wanted to put the capacitor on the low impedance side , let's say at 10Mhz, what would you do? Which value of reactance should be on the low side?


Il 27/ago/2018 03:55, "Chuck, N1KGY" <cwayers12@...> ha scritto:
Tom

When you measure VSWR you are measuring reflected power. The less reflected power, the lower the indicated VSWR. When you measure a transformer (or attenuator, or feedline, or any circuit element) with 100% loss, there is no measured reflected power. All of the forward power is absorbed by the circuit element and none is reflected. A VSWR bridge sees no reflected power and reports VSWR = 1:1.

WA8TOD



Re: uBITX on CW

ke4d@...
 

I've never had my uBitx on phone.  CW only. I do have a microphone but I'd have to look for it!


Re: End Fed antennas w/ uBITX #ubitx

iz oos
 

Please disregard my previous post as it was a comment on another thread!


Il 27/ago/2018 09:31, "iz oos" <and2oosiz2@...> ha scritto:

Hi Chuck, indeed I was thinking with the logic of building wideband transmission line transformers which cannot be easily built with such a high transformation ratio. As far as I understand you would put the capacitor at the antenna side. If I wanted to put the capacitor on the low impedance side , let's say at 10Mhz, what would you do? Which value of reactance should be on the low side?


Il 27/ago/2018 03:55, "Chuck, N1KGY" <cwayers12@...> ha scritto:
Tom

When you measure VSWR you are measuring reflected power. The less reflected power, the lower the indicated VSWR. When you measure a transformer (or attenuator, or feedline, or any circuit element) with 100% loss, there is no measured reflected power. All of the forward power is absorbed by the circuit element and none is reflected. A VSWR bridge sees no reflected power and reports VSWR = 1:1.

WA8TOD


Re: Harmonics measured by Warren. How bad?

iz oos
 

What you ask is a tunable pre selector. Simple schematics may be taken from the receiver preselectors by the MFJ. Take the components such as capacitors able to the voltage required. And see whether the insertion losses are acceptable. Besides external LPF (schematics on communication-concept site) I have done a rudimentary variable LPF with just a variable 2*450pf a T-130-7 and a six position switch. For what I can see with my poor instruments (cheap antenna analyzer, AD8307) the variable LPF seems not too bad, considering the problem is beyond the third harmonic.


Il 27/ago/2018 01:13, "Brent Seres" <brentseres1@...> ha scritto:
Okay
Here is another idea. Full disclosure, I'm not an engineer, and many here are much more knowledgeable, experienced and have far better test equipment than me. I do understand the basic math of resistance , reactance, resonance, etc. I also realize this idea is not in keeping with modern, minimal knob technology. Feel free to educate, debunk, etc...I won't take offence.

Would it be possible to construct a simple, tunable bandpass filter, to go in series with the antenna, or between the driver and the final. QRP, so old air variable cap should work. Just throwing the idea out there...

Brent
VE3CUS



Re: Fried irf510s replaced but

jfein2000@...
 

Thanks Allison, haven't checked the coils yet.  Finally got the rig back on line and operating.  I put in an inline fuse and blew four of them adjusting the bias and rv1.  The VERY best advise I have seen in the group website is the addition of the fuse.  If it helps anyone else I found through monitoring the current draw while adjusting the bias my current draw would climb on cessation of transmitting and could easily blow the fuse......or fry my irf510s.  I found by experimenting and blowing four fuses that the setting of the bias had to sync with RV1 or the current would jump on completion of transmission.  Finally found a point of balance.  I don't know if this is idiosyncratic to my rig or experienced by others.  Conrad's advice about q90 wax also spot on I have bough a few spare 2n3904s and add posts to mount them as I find it difficult to work with the smd pads with a soldering iron.

Cheers Jeff
VK3GMO
ex WA2GMO


Re: End Fed antennas w/ uBITX #ubitx

iz oos
 

Hi Chuck, indeed I was thinking with the logic of building wideband transmission line transformers which cannot be easily built with such a high transformation ratio. As far as I understand you would put the capacitor at the antenna side. If I wanted to put the capacitor on the low impedance side , let's say at 10Mhz, what would you do? Which value of reactance should be on the low side?


Il 27/ago/2018 03:55, "Chuck, N1KGY" <cwayers12@...> ha scritto:
Tom

When you measure VSWR you are measuring reflected power. The less reflected power, the lower the indicated VSWR. When you measure a transformer (or attenuator, or feedline, or any circuit element) with 100% loss, there is no measured reflected power. All of the forward power is absorbed by the circuit element and none is reflected. A VSWR bridge sees no reflected power and reports VSWR = 1:1.

WA8TOD


Re: uBITX on CW

SV9CVJ Nikos
 


Re: 4000 mile phone qso on 20m

Alex KA3BQE
 

I spent the first 10 years as a ham QRP and worked the world and I was lucky to have a dipole and vertical (vertical worked better). Now 40 years later I'm getting back in and going QRP w/ EFHW. 


Re: Let out the magic smoke...

Adrian Waiblinger
 

Be very careful playing on 160m in the uBitX stock configuration.  The PA easily puts out over 30watts with the second and 3rd harmonics to join the party as well.  You should have a fuse in-line to stop the fets letting out the smoke.  There is no ALC to tame the amp at low frequencies.  Plus with the small heat sinks the fets go into melt down quickly.

Fuses save the day.

I haven’t burnt out my pa when testing on 160m into a dummy load at 30watts.  But with a poor SWR I can see it won’t last.  

 I have blowed a few fuses when I over drove the pa  in my tests.

Regards 
Adrian 


On 27 Aug 2018, at 11:43 am, Gwen Patton <ardrhi@...> wrote:

I'll check the finals. I have some spares, just in case.

I'd love to be able to control the power out on the uBitX without opening it up and turning a trimmer pot. If it had a control for output power, I'd use it. The stock machine, as I'm sure you've noticed, doesn't have a way to reduce the output power.

So it is what it is. Perhaps I was naive that it wouldn't blow up while trying to tune for a few seconds.


Re: Harmonics measured by Warren. How bad?

Tom, wb6b
 

The problem with relying on tuners to cut harmonics is it is hit or miss. I have a L network tuner I use. Sometimes, on some frequencies, my antenna is in near prefect tune and the matching box is basically passing the transmitter output direct to the antenna. In that case the L network has no chance to act like a low pass filter and remove anything. Maybe there are other tuners that stay in circuit, even when the antenna is a match, with some resonance to possibility act as a band pass filter. 

Tom, wb6b


Re: Harmonics measured by Warren. How bad?

Brent Seres/ VE3CUS
 

Would something like this on the output help?

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.arrl.org/files/file/Technology/tis/info/pdf/8809017.pdf&ved=2ahUKEwjGlvW8m4zdAhUn54MKHSfJCSQQFjABegQIBxAB&usg=AOvVaw3uTeG3YM8UtUS_8W-P5N5V


Re: Harmonics measured by Warren. How bad?

ajparent1/KB1GMX <kb1gmx@...>
 

Bill K8UH,

I think part of the problem here is many get posting one by one in the Email
and from moment to moment they have at best a vague notion of whats
going on till it grabs there attention. The problem then information and
postings are history that has gone past them.

I seriously wonder how many see this in the web format where scrolling
back is as easy as the mouse wheel.    Even with the web form if it not the
top 20 active threads it goes into the second of nth page and gets lost there.

Its why stuff gets, needs to be repeated so often.  Maybe the wiki function need to  
be populated. 

Allison


Re: Harmonics measured by Warren. How bad?

Howard Fidel
 

John:
Unfortunately, my uBitx Raduino died,and i haven't had the time to fix it and test my circuits. I should get to it this week.However the simulations are clear, it will work. The fix though is to change the impedance to 25 ohms, of the filters, which allows the capacitor values to triple.That reduces the effect of the relay capacitance. The output transformer needs to be rewound, the filters changed, and a 1:2 transfomer added to get back to 50 ohms. That is the only artwork change, the transformer.

Howard
Quoting John KC9OJV <greusel@sbcglobal.net>:

Ashhar,

Did you see Howard Fidel's suggestion that the filters could be recalculated to account for the added capacitance of the relays? Original post and comments here #56495 ( https://groups.io/g/BITX20/message/56495 )
It's certainly an interesting idea- haven't heard of his theory yet being tested but even if not a complete solution it's another arrow in the quiver.

John
KC9OJV


Re: Let out the magic smoke...

Gwen Patton <ardrhi@...>
 

I'll check the finals. I have some spares, just in case.

I'd love to be able to control the power out on the uBitX without opening it up and turning a trimmer pot. If it had a control for output power, I'd use it. The stock machine, as I'm sure you've noticed, doesn't have a way to reduce the output power.

So it is what it is. Perhaps I was naive that it wouldn't blow up while trying to tune for a few seconds.


Re: Let out the magic smoke...

ajparent1/KB1GMX <kb1gmx@...>
 


Based on what you have told us.  Beats us.

Likely finals.
First without a load assure yourself the power supply is ok.

The easy test for fried finals is pull the wire that power them
(and them only). I think it s brown.

Also hint if you are running more than 10W on any band, surprised
you should not be when heat gets them.

Allison