[Lowfer] LW BCs tonite in EN90xn & recent LF bench tinkering

[Michael Sapp]

Jay: OK, I have read about the square wave usage. I can try that with the 
1,5 or 10MHz square wave output options of my Spectrcom receiver which is 
harmonic
rich. Building another filter an evening task  For the time being I want to 
tinker with the diplexer tuned circuit Qs as that should be a good learning 
experience.
The VLF end of the converter seems seems much improved from 5 to 100kHz with 
considerably less IMD products. Although recent rains may have lowered
the local noise level here as well.

Tnx for your input.  73  Mike wa3tts

----- Original Message ----- 
From: <jrusgrove at comcast.net>
To: "Discussion of the Lowfer (US, European, & UK) and MedFer bands" 
<lowfer at mailman.qth.net>
Sent: Saturday, May 03, 2014 7:22 AM
Subject: Re: [Lowfer] LW BCs tonite in EN90xn & recent LF bench tinkering


> Michael
>
> LO LPF generally not much value with a diode ring mixer ... the diodes are 
> being switched from full off to full on generating their own harmonics. 
> There may actually be some advantage to a square wave LO.
>
> I-F port diplexer is definately worth the effort.
>
> Jay W1VD  WD2XNS  WE2XGR/2  WG2XRS/2
>
>
>
>
> ----- Original Message ----- 
> From: "Michael Sapp" <wa3tts at verizon.net>
> To: <lowfer at mailman.qth.net>
> Sent: Saturday, May 03, 2014 12:53 AM
> Subject: [Lowfer] LW BCs tonite in EN90xn & recent LF bench tinkering
>
>
>> Hi All: Several LW BCs copied this evening, nice to see the T/A path to 
>> EU still open this late.....
>>
>> https://www.youtube.com/watch?v=HOE5jmqgC5E&list=UUfTfag2dJYGGilPLMs0uVXw
>>
>>
>> The LO filter is a recent add-on and looks like this....
>>
>> http://i1296.photobucket.com/albums/ag19/wa3tts/isotemp2_zps991e55f2.jpg
>>
>>
>> And the diplexer looks like this....
>>
>> http://i1296.photobucket.com/albums/ag19/wa3tts/DIPLXR_zpsb092e34e.jpg
>>
>>
>> I looked at the output on the HP141T SA with only the LO filter added to 
>> the mixer and the net effect was to lower the 2nd harmonic 3 dB but 
>> increased
>>
>> some of the higher order product levels several dB ---although still 
>> 30~40 dB down from the 3.0~3.5 MHz IF of the converter.  Perhaps a second
>>
>> diplexer for the LO would be a better alternative for mixer IMD 
>> improvement vs the LO filter, since the OCXO is already -44 and -62 dB 
>> down on 2nd and 3rd harmonic output on it's own
>>
>> (the harmonics regenerate anyway inside the DBM).....
>>
>> Also interesting to look at the IF xmas tree output on the SA and see the 
>> how sideband products cancelled in the DBM either side of the 2nd & 4th 
>> IF harmonics with the converter connected to the antenna....
>>
>> http://i1296.photobucket.com/albums/ag19/wa3tts/IMG_3760_zpsfcd93207.jpg
>>
>>
>> Sorry I did not get a image capture of the converter output on the SA yet 
>> with the diplexer in-line. It did show 30dB return loss from 1.7 to 30 
>> MHz on my MFJ-259B
>>
>> with the exception of being around 28 dB RL in the center of the 3.3 MHz 
>> IF passband.  Insertion loss looked to be about 1/2 to 1 dB range in the 
>> IF passband .  LO filter RL was 25dB at 3.05Mhz and
>>
>> 20dB at 3.0 MHz on the MFJ analyzer, so it still needs a slight capacitor 
>> tweek....
>>
>>
>> Sure felt good to melt some solder after several weeks of constantly 
>> jockeying federal forms in my not-so infinite "free" time.....
>>
>> Thanks for the bandwidth, 73  Mike, wa3tts
>>
>>
>>
>>
>>
>>
>>
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