[Lowfer] SIW in EN90xn & some antenna & filter measurements

[Michael Sapp]

Garry: OK, thanks for the reminder on 630m wspr. I've been testing the new 
300kHz LPF here and it is like 25~30 dB down at 475.7 kHz so I was not 
running a second receiver at 630M.
Guess I'll go back to WSPR2 tonite on 630m with my 500kHz filter and run 
more 300kHz LPF tests in daylight when all the local AM BC stations are at 
full power.

Total uVs on the EWE to the NE are 150,000uV and 45,000uV (@50 ohms) to the 
SW with no LPF's in line during daylight. Levels do drop considerably at 
sunset when many of the
local AM BCs reduce power (I have measureed something like 40,000uV and 
12,000uV range at night).

Daylight antenna rx power levels drop to 2,100uV SW and 6,500 uV NE with my 
500kHz LPF and 200uV to SW and 300uV to NE with the new
300 kHz LPF as measured with an Boonton CA-91 RF voltmeter, about 15 minutes 
prior to this e-mail....

With 20dB of gain from the W1VD design 2N5109 preamp, that provides 20,000 
to 30,000uV of total LF amplified signal level after the 300kHz LPF. A 3dB 
pad on the mixer input lowers the total rx signal level to the 10,000 to 
15,000 uV, which is -27 to -24.5 dbm range.  Having 47 to 50dB of dynamic 
range head room with a level 23 mixer sure helps to provide intermod-free 
performance below 300kHz....

For example, with the 500kHz filter and 6,500uV of total daytime LF/MF 
signal, the 20 dB 2N5109 preamp ups that total rx power level to 650,000uV 
and the 3dB pad before the mixer reduces total rx power to 325,000uV, which 
is slightly more than +3dBm total signal level the mixer is seeing in 
daylight receive conditions.  One can appreciate the need for an LF/MF 
optimized  +17 or +23 dBm level mixer with many nearby AM BC stations.....at 
night those total rx power levels drop by about a third, but are still 
fairly high.

Compared to the cost of college tuition these days, finding that old Boonton 
CA-91 on ebay for $50 and putting it to use sure has been a worthwhile 
educational investment....

73, Mike wa3tts






----- Original Message ----- 
From: "Garry Hess" <k3siw at sbcglobal.net>
To: "lowfer list" <lowfer at mailman.qth.net>
Sent: Wednesday, December 10, 2014 12:35 PM
Subject: Re: [Lowfer] SIW in EN90xn


> Thanks for another nice capture Mike. Hopefully the noise will die down 
> one of these nights. 474.2 kHz WSPR activity has been low and nothing 
> other than MP has been copied on 137 kHz. The lowfer watering hole does 
> have a handful of stations but more would be nice. The forecast for 
> Saturday here is quite mild so may finally get a chance to work on the 
> lowfer SIW slash code.
> -- 
> 73, Garry, K3SIW, EN52ta, Elgin, IL
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