This is a fairly broadband design with insignificant differences for C1,
C2, C3 and L1 between 144 and 148 MHz. They are bypass and shunt capacitors
and an RF choke; they are not part of a tuned circuit. You could actually
use the same values at 50 and 432 MHz just fine. You wouldn't even notice
any difference in gain.
The PGA-103 does not have an extremely low noise figure like an HJFET would
have, but you are probably not too concerned about that on FM. Back in the
70's people didn't even have 1 dB NF's.
73, Zack W9SZ
On Thu, Dec 12, 2019 at 9:51 PM Gregory Winters <greg_winters@hotmail.com>
wrote:
> Thanks for that!
>
> His design is at 144 MHz with values at 1000pF for C1, C2, and C3, and
> 56nH for L1. Not sure if that would change, or which way, for 146.5. A
> formula out there? Maybe the design just gets less gain as a consequence
> when up a bit higher, but still works (that's ok).
>
> But at $2 thats a worthy project. Yay!
>
> If its no good at 146.5 then I have a cheapie LNA for 2m SSB. Then change
> some values and try again.
>
> I'll use a sequencer at some point ($30) and I wasn't impressed with the
> cost of linears with preamps. A sequencer will handle this just fine. Much
> cheaper than a linear or a big LNA, and essential anyway if using a linear.
> How many Mirages out there have bad preamps due to RF sensing!?
>
> It may be unfortunately true that upping a LNA on FM may just raise the
> signal, but also the noise floor just the same. It might be my mobile and
> residential noise floor is just high. If so, I'd rather build something
> cheap than run a $120 LNA just to find that out.
>
> Thanks!
>
> Greg, K3RW
>
> Get Outlook for Android<https://aka.ms/ghei36>
>
> ________________________________
> From: Dennis Allen <N9TZL@outlook.com>
> Sent: Thursday, December 12, 2019 7:22:32 PM
> To: Gregory Winters <greg_winters@hotmail.com>;
> vhfcontesting@contesting.com <VHFcontesting@contesting.com>
> Subject: Re: 2m FM LNAs?
>
> Greg:
> I do not know what your level of construction skills are but you might at
> least google this and see what you think.
> Dennis Allen N9TZL
>
>
> Simple Cheap MMIC Preamps Who needs a GaAsFET? Paul Wade W1GHZ ©2014
>
>
> w1ghz@arrl.net
>
> ________________________________
> From: VHFcontesting <vhfcontesting-bounces@contesting.com> on behalf of
> Gregory Winters <greg_winters@hotmail.com>
> Sent: Wednesday, December 11, 2019 6:58 PM
> To: vhfcontesting@contesting.com <VHFcontesting@contesting.com>
> Subject: [VHFcontesting] 2m FM LNAs?
>
> I'd like to enhance 2m simplex abilities and pull in weaker SOTA
> activators. Often times they hear me but I do not hear them. Increasing my
> antenna capability would help (of course). But I can't run a beam mobile.
>
> I'm looking for a reasonable LNA to pull out these weaker ones on 146.52,
> etc. But many of the LNAs I see are for the SSB side of things.
>
> Is there a LNA that I could use for FM?
>
> Ideally I'd be able to use it mobile too. I run 65w on a 5/8s whip,
> seemingly everyone hears me, but I struggle to hear some of them. The
> Kenwood 2m mobile has an awful NF I guess, so I am hoping a LNA can help
> that.
>
> Ideas?
>
> Greg, K3RW
> CN85ro
> _______________________________________________
> VHFcontesting mailing list
> VHFcontesting@contesting.com
> http://lists.contesting.com/mailman/listinfo/vhfcontesting<
> https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.contesting.com%2Fmailman%2Flistinfo%2Fvhfcontesting&data=02%7C01%7C%7C98ae4ac940f1413c3bc708d77f7bb2d3%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637118041561664464&sdata=KRlG4t2dgjwEKGB%2F3R6vjNCDstIKcbhgKVgvUPZNHXo%3D&reserved=0
> >
> _______________________________________________
> VHFcontesting mailing list
> VHFcontesting@contesting.com
> http://lists.contesting.com/mailman/listinfo/vhfcontesting
>
_______________________________________________
VHFcontesting mailing list
VHFcontesting@contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting
|