VEry annoying I attached three things and none followed the post!

So 2n2222A datasheet
2n3904 data sheet
and picture of said amp built on Kitsandparts board.

On Thu, Aug 30, 2018 at 08:46 AM, Kees T wrote:

I was wondering about the reasoning behind using several parallel 2N3904 transistors in the uBITX circuit.....they are inexpensive, but why not just use a single 2N2222 ?

For the driver you need about 400mw and one 2n2222A would not do it maybe
as push pull as I've run them as linear that way for 500mw.

The big thing is the 3904 is high power?and trying spread the load. To me it
creates more issues.? Same for the pre-driver.

As stated before the 3904 peak HFE is at 10MA and for the 2n2222A its 150MA.
For a power amp diminishing HFR with increasing currents means you get non linear
operation.

However farhan has the bias so high the driver and predriver runs at AB levels.?

>>>the BFR106 has the dissipation, but the 3.5 to 5GHz Ft invites instability

No it doesn't as the amp is a resistive feedback amp and gain max is 18DB
if the device can do that.? A 3904 can but the gain corner is 8mhz and drops
from there to about 10db at 30mhz.? For that amp to hit 18DB at 28mhz the
device must have an FT of 1100mhz or higher.? Bipolars have FT as a limit
for common emitter amps.? For Q90 its works well.

For the predriver and driver part none of those listed are better than 2n2222A
Though the DXT2222 (ignoring footprint) is also good as it behaves like the
TO18 part at high currents.? Other parts are 2n2219A (same die as 2n22222A
in TO5/TO39 and can handle more power) but FT limited.? ?The classic 2n3866
is better but FT is 500mhz and the 2n5109 is better still.? This is from better to best.

I built an amp using a KITSANDPARTS board (5W CW AMP) with mods using a
2n5109 driving a pair of IRF510s.? The result is flat (within 2DB) power from
3 to 30mhz and at about 26db overall gain.? With 14DBM drive I get 10W and
at 20dbm its up to near 17W at 13.8V.? At 20V 20W is easy with additional drive.
The only changes were replace his 2219 with 5109, and lift the driver transformer
center tap to inject bias there.? Transistors are mounted on top as are the IRF510s
and the output transformer and bias transformer? also the bias network are on the
underside to allow?for heatsinks (board was designed to take BD139s).? Bias
anything in the range of 100 to 350ma was tried but about 180ma per mosfet
was about right for linear operation.

You need a driver that can product the desired gain across a decade and
the transformers have to be better.? The layout must be like its a VHF amp!

There are other IRF510 amps that do that or better!? MOSFETs have no FT
however impedance matching is a challenge regardless the part.

Allison

I have one of the Chinese tuners, with the plastic, variable capacitors, that I built from a kit.? I found the adjustments to be very touchy and not repeatable.? I have since replaced it with an?MFJ-9201, QRP Antenna Tuner.? It is well made and is a lot easier to use than the Chinese, kit tuner.

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?Wow, that's a pretty complicated printed circuit board....and we already have a ton ofproblems with one laid out by a fellow who has years of experience at it.....wish you good luck!!!? ?

cheers,

gordon

Yes, I think with some low pass, band pass filters it will be useable, especially on 20 and below. I still think it's amazing what can be packed in when one considers the price. When I started out, the cheapest way to get on the air was to get military surplus, in my case a 'wireless set #19' Cost me 50.00, which translates to about 320.00 today, covered 80/40, single 807 final, had terrible chirp, and you had to build a HV supply.

Next rig was a dx60/hr10/hg10. New worked out to about 300.00 CAD, or 1900.00 in today's money. Regardless of the growing pains, we've come a long way!

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Hey folks, ?I guess I need to put my oar in the water, too. ? :-) ? I can’t begin to thank you all for the diversity and variety of topics on this group. ?I admit that some went on to extreme limits, but the very breadth of them have provided me with lots of things to think about and learn about. ?I am grateful for the experts out there who continue to help those who are not so knowledgeable (and sometimes REALLY not so knowledgeable). ?You have made my day on topics well out of my comfort zone. ?Thank you … you know who you are …

Dear al,

The newest Power and SWR meter design and for sure home made, small and really accurate.
See for more information :
/g/RadioStuff

Also nice to see the one of a kind CWModem......
73' PD0LEW, Johan Holstein

Two questions:

When I tune in 10MHz WWV in LSB mode on the uBITX, the frequency reads 9.998.500.? Does it mean the rig is out of calibration or is it supposed to read like this in LSB mode?? I note that Fc-BW/2 is exactly what I'm reading on the display so it makes me suspicious.? Before I go through the calibration procedure and potentially screw things up further, I was hoping someone can confirm.

BTW, the calibration procedure on hfsignals.com just says find an AM broadcast signal and says nothing about the mode the rig is set to (USB/LSB).? Doesn't the mode matter during calibration?? Thanks!

73 Mike KK7ER

P.S. How 'bout a free PCB for the help?? I'm looking to build this: /g/BITX20/message/54034

I have a T1 its the ideal pocket sized ATU.? Excellent battery life? I replace
it once a year on general principle..? I believe it can tune?a nail on 80m.
For less than 12W its bullet proof L tuner.? It tunes up well even at 1W
and less.? It does so in less than 5 seconds.

One hard note while they rate it for a max of 20W I've blown detector
diodes?on 40M for some antenna cases.? Its related to power under
some reactive condition where the voltage at the atu output exceeds
diode tolerance voltage.? It does not show tuning a HW wire at 15W.?
It only takes out one diode of the pair.

That said for under 15W its easy to use and works very well.

I use it with the:
KNQ7A (40M) SSB
Slop bucket 20 SSB
Argonaut 505 (all bands) SSB mostly
Tempo-one QRP tube radio (modified,? 12BY7 driver as final about 4-5W)
HB 40M SSB
HB20M SSB
HB15M SSB
HB 10M SSB
Kistandparts 1W CW
WM20? SSB
PSK20 PSK31
FT817 with matching interface cable HF

Allison

Allison,

Yup, the blowby around the LPF's is at the top of the list of things to fix.
Most forum readers seem to have that one figured out.
I did say "should" not "will" for a reason.

Also, as you originally brought up long ago, those 7dBm mixers are seeing nothing like 7dBm
from the si5351, which means they are overdriven at lower signal levels than they should be.
Worth keeping in the list when talking about trouble around those IF stages.

Jerry

On Thu, Aug 30, 2018 at 11:32 AM, Gordon Gibby wrote:

And I've learned a TON!!!

I think that's what it's all about.....intended or not.?

73 Kees K5BCQ

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yup -- cheap radio, early attempts!!? ?the key is to offer constructive improvements by spotting where signals are going the wrong way.? ?Perhaps Ashar can make the needed improvements.

?

I'm a lot happier nowthat I know I can get the thing to? basically work on 80/40/30 --- the prime bands for digital emergency comms for me.? ? The ability to switch so rapidly from receiver frequency to another is a vast asset for an ALE system.? ?I may hang a LPF somewhere just above 20 M on the output and that should clobber the remaining spurs for me from 80/40/30/20 meter digital operations.??

And I've learned a TON!!!

Gordon

I can't comment on ft8, but I managed southern Ontario to northern Brazil with my bitx40 on 40cw and end fed wire

If the ATU is close to the antenna I would opt for an auto. If you use the atu close to the rig I would prefer the manual.

On Thu, Aug 30, 2018 at 11:01 AM, ajparent1/KB1GMX wrote:

Its all related to board layout and other paths like shared?
and unfiltered power distribution.? A? signal in one area presents it self at some level elsewhere
where its not wanted.

Notes are coming faster than I can read them..............

There are also simple #43 material ferrite chokes which can be added to reduce conducted RF on power source lines with no loss in DC current capability.

I still believe "there is a pony out there" .....small handful of parts and a good dual relay switched LPF board.

73 Kees K5BCQ?

On Thu, Aug 30, 2018 at 10:42 AM, ajparent1/KB1GMX wrote:

Reason is the 45mhz amp picked up stuff from the power amp
and adds it to the output creating a greater number of products related to
harmonics of the lower bands and the unfiltered products of the higher bands.

Allison,

THAT is a problem.

Since there is not much shielding between sections on a uBITX, wouldn't it help going to RD16HHF1 (or RD15) part, so at least the MOSFET Source lead can be solidly grounded vs tying it to a "heatsink antenna". I would also make those MOSFET leads ALL "REALLY short".

Another thing about RF power lead bypass caps .....100nF is good but they also ought to have a 1nF-10nF cap in parallel.

73 Kees K5BCQ

On Wed, Aug 29, 2018 at 08:53 PM, Jerry Gaffke wrote:

The strength of the spur will depend on how? loud you yell into the mike? (and thus overdrive the mixers).
I believe it is typically 30dB down or so.

The key is since there is excess IF gain yelling is not needed.? The last mixer is
over-driven by anywhere from 7 to 12 DB for openers and even pushing a smaller
amount gets you to more of same.

The closer we looks the worse it is.? Its all related to board layout and other paths like shared?
and unfiltered power distribution.? A? signal in one area presents it self at some level elsewhere
where its not wanted.

Allison

Jerry,

I also said that.? However it was assumed the 20M LPF worked as we found
out later it does not.

The big LPF (9 element at T1) however has a corner frequency of about
33mhz (33.68 mhz in mine) and that is the 3db point so below that its an
open pipe.

Rather than hash minor points the issue is below 20mhz the output filters
do not work as designed.? Warren showed a lot of work to prove that.? ?
Above 20mhz there is no filtering.? Spurs below? the cutoff for the 10M
output LPF and the other 33mhz filter have a unfiltered path.

Now we add to that high power output on the lower bands tends to couple
into the IF especially the 45mhz IF and contribute new tones to the mix
increasing the products at the output.? Several of us have seen that but?
it was not understood why.? ?Best example is 80M SSB at 10W or more,
Not only does one see harmonics leaking by the filter but there are a
host of other seemingly random products that are the result of the output
signal and harmonics plus 45mhz and OSC2.? Push just a little for say
15 to 20W and those grow alarmingly.

Allison

First SSB contact with new uBITX was with JE6EHP on 20m with an end-fed random wire. Nice long chat. Well over 8,000 Km. -Don