[Lowfer] reeLRe: EAR rx on FT-817

[Michael Sapp]

Zack:  Working better than I expected although my optimized LF converter 
would be my preference.

 I am still investigating how sensitive the FT-817 is using this e-probe > 
LPF > preamp> 3dB pad or diplexer arrangement. But I was surprised it worked 
as well as it did on WH2XXP on 2200m last night  and EAR on 188.83 kHz this 
afternoon.  Note that the IPO needs to be "selected"  (preamp off in the 
FT-817) to hear anything at LF/MF.  An LPF seems to be the key to preventing 
AM BC overload and having the FT-817 see a reasonable 50 ohm match in the 
pass band for the receiver to respond favorably at LF and MF.

With the TCXO in the FT-817 it seems stable as shown by flat-line QRSS on 
the EAR in the waterfall.  So it saves the cost of an OCXO LO in an LF/MF 
converter,,,,

I tried playing with the alignment menu in the FT-817 but the low band IF 
sensitivity adjustment and that did not seem to make any difference. I threw 
the 2N3904 preamp together as a quick test last night.  A lower-noise 2N5109 
would be preferred.  The 2N3904 preamp is basically the same as the one 
shown on page 43 in this month's (Jan) QST but I chose 4.7uf input and 
output coupling caps to be 1 ohm of reactance at 137 kHz and went with 
better B+ filtering for the LF application.  The 1N4148s are for protection. 
You would not want to amplify a 100,000uV AM BC signal by 20dB and inject it 
into the FT-817.....so the preamp is only being used after the BC LPF....

I will let the FT-817 run this evening on the 2200m band to see how it hears 
under the WA3TTS/2 call and post any antenna changes (e-probe vs EWE, etc.) 
to KST chat kHz page....

Agreed the FT-817 makes a good uwave transverter IF radio.  Having used a 
single diode mixer in my 10GHz waveguide transverter for several years out 
of simplicity, I learned that one could overcome sensitivity issues with 
enough preamp gain. There are other shortcomings to that approach (port 
isolation, IMD, etc.) but it works for casual to moderate-serious u-wave 
communication.  Seems to apply to the FT-817 at LF/MF as well.

At this point I need to find the right gain and NF combination for the 
preamp with the FT-817 at LF/MF to further refine the performance.

73 Mike wa3tts

----- Original Message ----- 
From: "Zack Widup" <w9sz.zack at gmail.com>
To: "Discussion of the Lowfer (US, European,& UK) and MedFer bands" 
<lowfer at mailman.qth.net>
Sent: Thursday, January 25, 2018 4:27 PM
Subject: Re: [Lowfer] EAR rx on FT-817


>I got an FT817 recently but haven't used it on LF yet. With the setup
> shown in these drawings does it seem to do OK? I'll have to play
> around with it.
>
> It does well as a microwave IF using 144 MHz. Neat little radio!
>
> 73, Zack W9SZ