[Lowfer] ref FT817 WD2XKO WSPR-15

[Howell, Laurence J]

Dex - I had the same problems - the drift was a little excessive but given the small form factor it isn't surprising and given mine has been dropped out of a moving aircraft - frozen to -67C and heated to probably the same, shot at, used as an offensive weapon, ad hoc body armor - etc it does pretty well :-) 

 I shoved in the TXCO and it didn't really make a lot of difference - I did the same and reduced the Voltage and after an initial ramp up/down in freq was good enough for transverting  down with at 5MHz mix source at dot 30 . Awful Rx at 500 and worse at 137 (lots of IM at 500 and deaf at 137 without 20-30dB of pre frontal lobe again in this environment)

But it did work Italy barefoot on CW from Namibia on a ground plane back to Italy on 6m TEP, and also ops from Mongolia  so its still one of my favorite rigs :-) 
Laurence KL 1 X


-----Original Message-----
From: lowfer-bounces at mailman.qth.net [mailto:lowfer-bounces at mailman.qth.net] On Behalf Of Dexter McIntyre W4DEX
Sent: Wednesday, January 30, 2013 2:43 PM
To: Discussion of the Lowfer (US, European, & UK) and MedFer bands
Subject: [EXTERNAL][Lowfer] WD2XKO WSPR-15

One more sequence from the drifter then QRT.  Storm line is getting 
close and winds already gusting to 30+ mph.

I've spent way to much time trying to reduce the drift in the old 
FT817.  I really don't need to be improve it for what I mainly use the 
rig for.  It's just one of those problems that isn't necessary to fix 
that turns into a time consuming challenge.  I've tried running the rig 
with a fan blowing on it, running it with the cover off, with and 
without fan, and trying to insulate the tiny plug in reference 
oscillator board from the chassis heat plus some I've likely forgot 
about. But what has come as close to stabilizing it at much as anything 
else was applying a hint from Mike, WA3TTS.  He informed me that the rig 
has an internal voltage regulator that reduces the input to 9.6 volts.  
I assume it was designed to work on that low of voltage because of it is 
capable of operating from an internal 12 volt battery pack.  With 13.8 
volts from a 25 amp Astron there was more heat being dissipated from the 
voltage regulator than from the radio being in transmit mode.  I put the 
covers back on the radio and added 6 power diodes in line with the 13.8 
volts then measured 9.4 volts at the radio.  It seems to work well at 
that voltage and the WSPR-15 drift is alternating between 1 and 2 Hz per 
15 minute sequence.  Not bad for a $75 radio with bad final FETs and no 
TCXO. 

Dex
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