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[moved] 6m pre amp

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Stu, MM0BSM

Sat Jun 20 2009, 11:07AM
A friend has a few yu1aw pre amp boards and all parts for sale if anyone is interested drop me a mail and i will put you in touch

pics on site below


hope to build one in next few days myself

Stu.bsm AT btinternet.com
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Stu, MM0BSM
Mon Jun 22 2009, 08:29PM
Stu, MM0BSM
Registered Member #66
Joined: Thu Mar 20 2008, 05:46PM

Posts: 20
some more pics added
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Stu, MM0BSM
Sun Jun 28 2009, 07:51PM
Stu, MM0BSM
Registered Member #66
Joined: Thu Mar 20 2008, 05:46PM

Posts: 20


added some more pics of nearly finished board only needs 1 smd cap and time to finish
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Paul, GW8IZR
Sat Jul 04 2009, 08:55AM
Paul, GW8IZR
Registered Member #49
Joined: Wed Mar 19 2008, 09:51AM

Posts: 10
Hi Stu, kit arrived quickly and the board is very nice quality. Construction was straight forward and it worked fb.

uncased on the bench S11 35db and S21 21.3db, +10dbm input results in just under +30dbm out! so it shows good prommise.

It was easy enough to get it working on 70MHz as well.

All in all a nice little project.

Regards Paul



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Roger, G4OCO
Tue Jul 07 2009, 12:02PM
Roger, G4OCO
Registered Member #225
Joined: Thu Apr 10 2008, 10:28AM

Posts: 5
Paul

What did you have to do in order to make the preamp work effectively on 4 mtrs, shorten the coils?

73

Roger G4OCO
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Paul, GW8IZR
Wed Jul 08 2009, 07:26AM
Paul, GW8IZR
Registered Member #49
Joined: Wed Mar 19 2008, 09:51AM

Posts: 10
It tuned OK with just minor changes to input matching, Changed L’s to 10t and C reduced to 82pf resulted in a rough and ready input RL of 20db. I didn’t bother trying to improve on that as it was good enough to prove the point. Gain at that was fine (same as measured at 50MHz) and even without test gear would have been OK tuned for best “off air” with a weak beacon etc.

I’ve decided to re do it later with a broad band match to cover 6 and 4 and I’m sure it will still have a NF much lower than terrestrial noise even here in rural GW – which means good enough.

HTH
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Ken, G4IGO
Wed Jul 08 2009, 12:29PM
Ken, G4IGO
Registered Member #31
Joined: Tue Mar 18 2008, 08:16PM

Posts: 62
Hi - am putting my preamp together - now looking for fit it inot a box and tune it up - more soon.
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Peter, PA2V
Tue Jul 14 2009, 07:15AM
Peter, PA2V
Registered Member #76
Joined: Fri Mar 21 2008, 04:20PM

Posts: 21
Finished the preamp. With my HP noise figure meter it showed 23.8 dB gain and 2.1 dB NF. Funny to see that with an open case the NF was a little worse. Try to tune it when the case is closed
Nice amp. With the 2.1 dB NF most commercial transceivers will gain 4-6 dB improvement. Don't forget to put an attenuator between the rig and preamp. The 23.8 dB gain is to much to put into your RX. 73,
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Zaba, OH1ZAA
Tue Jul 14 2009, 02:27PM
Zaba, OH1ZAA
Registered Member #123
Joined: Thu Apr 03 2008, 02:54PM

Posts: 25
Has anyone tried the PA3BIY-design on 50 MHz? Ordered a set of PC-boards through OZ1PIF and will try to modify it for various bands --- Measured 0.3 - 0.4 dB NF is far too good to make much improvement on the lower VHF-range, but in any case it should not add any noticeable noise either --- 73, "Zaba" OH1ZAA/OHoMZA ---
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Zaba, OH1ZAA
Tue Jul 14 2009, 02:41PM
Zaba, OH1ZAA
Registered Member #123
Joined: Thu Apr 03 2008, 02:54PM

Posts: 25
To be more precise: of course a NF = 0.3 dB will make a lot of improvement over an insensitive input, but not so much compared to a NF = 2 dB amplifier on 50 MHz, where the sky temperature is mostly over 3000 K --- When measuring NF´s with high input SWR´s it is good to study thoroughly the remarks by PA3BIY in the DUBUS/2002 article. The ATF-54143_preamp can be tuned for low input SWR (a design with high input SWR is not bad at all, but it is hard to do an accurate NF-measurement) --- 73, "Zaba" OH1ZAA ---
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