[Hammarlund] HQ-200 Low Sensitivity

Thu Sep 16 14:24:05 EDT 2010

Sounds like a plan Bill.

The 6SB7Y is a big improvement over the 6K8 and 6SA7 mixers commonly used, 
it generates about 1/4 the noise and was developed for the early 42-49 mc 
area FM broadcast band. I use them often in various radios where I dont want 
to make obvious modifications.

Then changing to a 6SG7 in the RF stage in place of the 6K7, 6SK7, 6SS7, 
etc. That swap involves minimum change if any.

The combination really wakes up those oldies from roughly 12mc and up.

Bill Orr wrote a CQ article for the NC-240D which is applicable to many sets 
that use the 6K8. The 6SB7Y is a direct swap for a 6SA7 but watch out for 
whats on pin 1 of 6SA7GT  radios; some use it as a B+ tie point and you wind 
up with a suprise when grabbing the metal shell! This can happen when 
swapping any glass with a metal octal tube which uses pin 1 to ground the 
shell.

----- Original Message ----- 
From: "Bill Stewart" <cwopr at embarqmail.com>
To: "Rodger Singley" <rbsingl at ilstu.edu>
Cc: "hammarlund" <hammarlund at mailman.qth.net>
Sent: Thursday, September 16, 2010 1:56 PM
Subject: Re: [Hammarlund] HQ-200 Low Sensitivity

> Hi Rodger & Carl,
>
> Rodger:
> Thanks a lot for your info. I tried a couple diff. 6C4s from my limited 
> stock, but only a small change in sensitivity was noted. However, I think 
> the voltage measurement at the 6C4 grid (pin 6) points out your comment 
> about the injection voltage. I got the following voltage readings 
> (Heathkit V-6 VTVM, arbitrary tuning capacitor setting):
> .54-1.6 Band  -9.0
> 1.6-4   Band  -7.2
> 4-10    Band  -3.4
> 10-30   Band  -2.0
> 20BS          -2.0
> As you tune the main tuning capacitor, the inj. voltage changes. And as 
> you would expect, the inj. voltage is at its lowest 
> value...around -1.34vdc, at 10 mhz on the 10-30 range...the area with the 
> lowest sensitivity and goes up to around -3vdc as I tune up into the 10-30 
> mid-range area. These values are in spec, according to the manual(-1 to -9 
> vdc). I guess, when I get a better stock of 6C4s I can try each one for 
> the most inj. voltage. Anyway, I guess this could indicate that the HFO is 
> operating in spec...but I can't imagine a new HQ-200 performing this badly 
> in that area of the range so I'm thinking there must be something else 
> amiss. I also tried a 6BE6, but no difference. I'll try a few more tubes 
> in the front end just for curiosity. I did check the tubes on a Hickok 
> tester, but that doesn't always tell the whole story.
>
> Carl:
> Many thanks for the suggestions on the tube mfgrs. I'll be looking for 
> those brands. I was glad to find that my newly acquired NC-125 uses a 
> 6SB7-Y instead of a 6C4. At least I hope that's good. I have several 
> Hammarlunds, so I better stock up on 6C4s.
>
> Thanks to you both for the help and suggestions.
>
> 73, Bill K4JYS
>
> ----- Original Message -----
> From: "Rodger Singley" <rbsingl at ilstu.edu>
> To: "Bill Stewart" <cwopr at embarqmail.com>, "hammarlund" 
> <hammarlund at mailman.qth.net>
> Sent: Thursday, September 16, 2010 9:27:57 AM
> Subject: RE: [Hammarlund] HQ-200 Low Sensitivity
>
> Bill,
>
> The first thing to suspect on any of the Hammarlund HQ series with a 6C4 
> HFO is the tube.  You may need to try several to find one that works well 
> in the receiver and putting in a brand new tube is no guarantee that this 
> is the "best" tube for the receiver.  Low HFO injection will greatly 
> reduce mixer gain and typically problems with the 6C4 are more prevalent 
> as the frequency increases.  The 6BE6 may also be contributing to the 
> problem but the 6C4 is always a prime suspect in Hammarlund receivers. 
> Your HQ-100 may have the same problem.
>
> Rodger WQ9E
>
>
> -----Original Message-----
> From: hammarlund-bounces at mailman.qth.net on behalf of Bill Stewart
> Sent: Thu 9/16/2010 7:54 AM
> To: hammarlund
> Subject: [Hammarlund] HQ-200 Low Sensitivity
>
>
>
> I recently acquired an HQ-200, which is sensitive on all bands except the 
> 10-30 mhz range. For example, WWV is S-9 at 10 mhz on the 4-10 mhz range 
> but only about S-3 at 10 mhz on the 10-30 mhz range. It is more sensitive 
> in the mid-range area, say 12-21 mhz, with some SWBC stns reading well 
> over S-9. Generally, the sensitivity seems to be real low at both ends of 
> the 10-30 range. The 20BS range seems to be fairly sensitive. I have gone 
> thru the alignment and only minor adjustments were needed for peak 
> readings. The IF is on the high side per the aux. rcvr.  A while back I 
> had a similar problem with a HQ-100, which we discussed here...but in that 
> case I temporarily shelved it due to a stuck slug. It also had low 
> sensitivity on the 10-30 mhz range. Is this normal for the HQ-200/100 
> rcvrs. Is anyone using a HQ-200 and can tell me how the sensitivity is on 
> the 10-30 range?
>
>
>
> I also noticed, that there are some differences in my rcvr from the BAMA 
> schematic (the BAMA info is issue 1 of the manual). A couple noticed are 
> tandem pots on the sensitivity control and a piece of coax going from the 
> ant. trimmer capacitor to the main tuning capacitor. These two items don't 
> show up on the BAMA pix. Does anyone have a schematic they could send me 
> that would fit my rcvr (s/n 36031666).
>
>
>
> Any help would be greatly appreciated. Thanks..73 de Bill K4JYS
>
>
>
>
>
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