[HBR] 160 Meter Coils

[Hopperdhh at aol.com]

Tom,

What frequency is your second conversion crystal?  That is, is it 1710, or 
what?  Also, what is your 1st IF frequency?  Also, what is the capacitance range 
of the tuning capacitor you are using, or what is the part number?

BTW about 69 turns of no. 26 on the 1 1/4 inch polystyrene forms will cover 
the entire 160 M band if your cap is the 1461-BS.  I believe there were several 
different capacitors over the years.  I tried some experiments on the 
Q-Meter.  The capacitance range for the above coil was 62 to 78 pF to tune 1.79 to 
2.01 MHz.  Interestingly, taping the coil over with Scotch no. 33 black tape had 
negligible effect on the Q or distributed capacitance.  Distributed 
capacitance doesn't seem to be a factor.  I measure only about 2 or 3 pF for the coil 
alone.  Boy, the Q of these coils are definitely high -- about 175 on my 
Boonton 260-A!  No wonder peaking up the front end can make or break the receiver -- 
so to speak.

Up till now I have only been talking about the signal tuned circuits.  The 
oscillator is of course another problem, but as I said earlier, that is 
definitely doable.

  Tracking is another issue.  That's one of my old hobbies -- doing those 
calculations.  Given the great difference between the signal range and the 
oscillator range we may have to use a padder (a "real" series padder) in the 
oscillator circuit.  That's still doable, I think.  Man, I wish I hadn't brought this 
tracking issue up!  I'll try to tackle that one tomorrow.

I guess I need to build a receiver to try out some of this theory!  This 
wouldn't be my first receiver project lest you start flaming me, but it would be 
the first of the Crosby brand. 

There is a bridge-T filter circuit on page 51 of the August 1967 QST.  It is 
used to reject 2496.5 KHz from the desired 2950 KHz signal.  Something like 
this may be used to trap the IF feedthrough on 160 in the HBR.  Or you could 
just put a series tuned circuit somewhere to shunt the IF frequency to ground in 
the front end.  Yes, I know this is tricky.  Might just require some 
experimenting!  Don't worry about crossing this bridge (pun intended!).  We may never 
get there!  It may turn out to be a non-issue, lets hope.

Dan K9WEK










In a message dated 12/26/2006 6:37:06 PM Eastern Standard Time, 
daileyservices at qwest.net writes:
Jay,

Thanks for the analysis - I did a far less technical measurement, and you're
right on the money.  The guy who originally wound my 40, 20, and 1 of the
80m coils wasn't a neatness freak, so MY 80m coils are neater and easier to
use emperical data upon.  I'm gonna' try to make some 160m coils, using 28
or 30 ga wire (smaller wire takes up less space), and just go for PART of
the band to begin with.  A very good point, brought up in this thread, is
that 1.8 mc is not very darned far from the 1.7 mc already used... so it's
possible that it's not gonna be real great, but what the heck... let's try.

When I was given my HBR-11, it was possessed of many problems, was missing a
tube, had NO identification as to what kind of radio is was (or it's origins
or inspiration), and it's since become a labor of love.  I was given the
original QST articles (for the 11 and 8), original cut-sheets on the IF
cans, and Variable Cap, and a set of HBR Notes.  Those enabled me to
resurrect this one (I even found the guy who built it).  I know that mine's
not as pretty as others'... and it still has a bit of mechanical
non-stiffness to work out, but it WILL be alongside my 1954 Heathkit AT-1 on
Straight Key Night, keyed by a 1939 McElroy Deluxe 300 key, and listened to,
via some Telephonics headphones from the back of a Consolidated PBY
Catalina, that flew with one of the famous BLACK CAT SQUADRON's out of
Tacloban, Leyte, during WW-II.  I think that the rig is historically proper
for the occasion.

Besides... They make the right smells.

Tom - WØEAJ

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