[Boatanchors] HQ-180 bandwidth

[D C *Mac* Macdonald]

 <426547.39477.qm at web52904.mail.re2.yahoo.com>
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Commonly called "swamping" resistors.  When placed in parallel
with a tuned LC circuit=2C they lower the overall "Q" thereby
widening the response.
=20
I had an NCX-5 transceiver that had its TX output go a bit
low while all other bands were good.  It was several years
before I looked at the schematic one more time and noticed
that there was a swamping resistor across one of the coils
in a driver stage.  I think maybe it was supposed to be
around 4.7k.  Eureka moment occurred when I remembered
the basic electronics from USAF school that talked about
using swamping to increase bandwidth.  I removed the
resistor and found that it had gone down to something
around 50 Ohms or so.  No wonder I had low drive!  It
appears that it was added to reduce the amount of drive
on 40m because when I keyed up with the resistor out
of circuit=2C way too much drive.
=20
73 - Mac=2C K2GKK/5
(Since 30 Nov 53)
Oklahoma City=2C OK



> Date: Fri=2C 25 Sep 2009 08:54:18 -0700
> From: gzook at yahoo.com
> To: boatanchors at mailman.qth.net=3B wc4r at live.com
> Subject: Re: [Boatanchors] HQ-180 bandwidth
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> In the 75A-2 and 75A-3 Collins widened the i.f. bandwidth by adding 100K =
resistors across the i.f. transformers. To "narrow" the bandwidth the manua=
l says to remove the resistors and then retune the i.f. stages. The result =
was reducing the bandwidth from 4 kHz to 2.4 kHz.
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> This might work in the HQ-180 if it is desired to widen the response. You=
 might have to "play around" with different resistor values to achieve just=
 the bandwidth required. If the resistors were "tacked" onto the terminals =
of the i.f. cans then they could be easily removed to change the receiver b=
ack to the original configuration.
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> Glen=2C K9STH
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> Website: http://k9sth.com
>=20
>=20
> --- On Fri=2C 9/25/09=2C Joe Roth-WC4R <wc4r at live.com> wrote:
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> I have a Hammarlund HQ-180C=2C all stock. Is there a reasonable way to ch=
ange the 3 KC receive bandwidth to 5 or 6 KC? I don't want a butcher job. S=
omething clean & reversible.
>  		 	   		  =