[Lowfer] SIW in EN90xn

[Michael Sapp]

Thanks Garry: My issue with the furnace is just thermal drift as the radios 
are just a few feet away and the large nearby btu rise causes a half to a 
few Hz drift depending on the radio used.  The FT-817 stays within a half Hz 
with it's optional TCXO installed through home heating cycles,  but it has 
less dynamic range and wider filters than my FT-847.....

The FT-847 has a Collins 300Hz cw filter, I used it and the 25Hz audio DSP 
to capture SIW on .185 last nite.  No xtal heater in the FT-847 (actually 
never thought to try that til now) but I made small foam booties for all the 
xtals in the 847 and installing them does help as the internal fan in the 
847 draws air across them.

I scrounged an old xtal heater out of a scrapped NTSC exciter and use it in 
my modified Heath HD-1420 VLF converter. Not much drift on that oscillator 
in the Heath converter but it is a few Hz off 3.500.000, which I should 
address one of these days with a better quality and lower value trimmer 
cap....

Between the TCXO in the FT-817 and the xtal heater in the HD-1420, QRSS60 is 
doable with reasonable results.  With the FT-847, QRSS30 Slow  is a 
practical limit, except for the few days in the spring and fall when the 
indoor temperature is very stable....even then QRSS60 has a bit of a slope 
to the capture view....

I know GPS reference locking is the way to go, but wanted to see what was 
possible at the ham shack test bench without it....

73, Mike wa3tts

----- Original Message ----- 
From: "Garry Hess" <k3siw at sbcglobal.net>
To: "lowfer list" <lowfer at mailman.qth.net>
Sent: Saturday, November 09, 2013 7:43 AM
Subject: Re: [Lowfer] SIW in EN90xn


> Mike,
>
> Thanks for the nice lowfer capture. Got a new high efficiency furnace here 
> a year ago and have to turn off the blower motor when monitoring below 100 
> kHz. Fortunately it doesn't seem to bother NDBs, lowfers, etc. higher up.
>
> -- 
> 73, Garry, K3SIW, EN52ta, Elgin, IL
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