Another K1 10 meter project

[Bill Cunningham K4KSR]

I'm launched on experiment to put K1 on 10 meters -- using 26.170 MHz xtal
at Wayne's suggestion (and generous contribution).  This should make the
whole project easier with lower frequency crystal and more premix output,
but I've run  into a snag and seek some advice.

Instrumentation here is pretty crude -- RF probe and HF receiver.  RF probe
uses 1N914 vice 1N34A and that makes a difference in readings for  low level
signals.  10 meter filters are built as Band 1 on a KFL1-2 board with 80
meters working like gangbusters as Band 1, my basis for comparison --
acknowledging potential difference in freq response for the probe.  The
premix filter is same as for 17 meters,  peaks nicely and right mixing
product verified with HF receiver.  Bandpass filter and RF board mods follow
design by Stephanie Maks, VA3UXB.  This includes change to R11 on RF board
and absence of L-section at output of BPF.  For now, the output filter is
jumpered across - just seeking raw output into dummy load.  Best I can
achieve is a hair under 200 mW output. That level does peak with slugs in L7
and L8 very near all the way down.   No problem hearing low level 10 meter
signal generated in shack.

Signal is dying either within the BPF or from mismatch at its output.
Comparison with 80 meters yields 1.06 volts at test point TR1 for 10 meters
vs 0.28  volts for 80 meters. The 80 meter signal drops to 150 mV at test
point BPF, but the 10 meter signal drops like a stone to 16 mV at the same
point, so difference in RF probe freq response cannot be an issue.  I'm
stumped over great difference from Stephanie's results.  Caps in the
bandpass filter are high quality from Elecraft. My only immediate source for
filter changes, however, is limited to Radio Shack - grand variety and
questionable quality.

Anybody else been down this path and have ideas?

Bill Cunningham
K4KSR

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Stephanie Maks]

Hi Bill,

I found that jumpering the BPF or even the LPF when testing, gave me  
results similar to what you are seeing.  I didn't start to see useful  
results until I had all the parts for all three filter sections  
completed.  Do you have the LPF set up completely?

I'm not in a position at the moment to test my K1 with a RF probe,  
too many other projects on the workbench right now so I can't compare  
the values along the TX path with what you are seeing.

There's one other thing...

I was looking at some digital photos I took of my K1 RF board and it  
looks like I removed R31 and R32 (they are in parallel with each  
other and sit between the Driver output / PA input and ground - see  
pp.79 in the K1 manual) but I don't have anything in my notes about  
it.  I don't remember removing them, but I know I had a few late  
nights where I was trying everything I could think of, to get the 10M  
board to work.  I thought maybe I had moved them to the bottom of the  
RF board, and/or replaced them with another value of resistor, but I  
just had a quick look at the bottom of the RF board and found that  
R31 and R32 are in fact missing.

I apologize for the mistake / omission in the information I posted.

73 de Stephanie
va3uxb
K2#5311 - K1#2132


_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com