[Hammarlund] hq-145a specification

[Richard Knoppow]

    That doesn't sound right. 25db is only about 20:1, a double 
conversion receiver even with just a single RF stage should be 
better than that. In fact, the RGB, a militarized version of the 
HQ-120-X has about 40db of image rejection at 20Mhz according to 
the chart in the handbook. At 30Mhz its about 22db. This is very 
good for a single conversion set with a single RF stage and 
455Khz IF. A double conversion receiver with a 3Mhz first IF 
should have something like 50db or more rejection at 20Mhz so I 
am suspicious of the value.
     Eliminating the second IF stage may result in an improvement 
in the linearity and noise of the RF over a two stage RF. The 
price is increased images. There is a price to be payed for 
everything, an additional stage of preselection has some faults 
while curing some problems but the extra conversion stage has 
another set of vices all its own.

On 11/5/2019 9:25 PM, Arthur Delibert wrote:
> Fred Osterman's book "Shortwave Receivers Past and Present" lists image rejection as >25dB at 22 MHz.  Also notes that the receiver is single conversion below 10 MHz, which suggests that lower than that, you may be seeing images of the stronger shortwave stations 910 kHz below their actual frequencies.  The SP-600, which was Hammarlund's top of the line receiver, dealt with that problem by having two RF stages; so you may want to add a preselector as a way to get rid of the problem.
> 
> Hope this helps.
> Art, KB3FJO
> 
> 
> ________________________________
> From: hammarlund-bounces at mailman.qth.net <hammarlund-bounces at mailman.qth.net> on behalf of Fernan Bolando <ve4feb at gmx.ca>
> Sent: Tuesday, November 5, 2019 2:04 PM
> To: hammarlund at mailman.qth.net <hammarlund at mailman.qth.net>
> Subject: [Hammarlund] hq-145a specification
> 
> Hi all
> 
> I'm not sure if i posted this already some place else, but...
> 
> I was wondering if any knows or can guesstimate the specification
> of the HQ-145a in terms of the following parameters
> 
> 1. Dynamic Range
> 2. Image Rejection Ratio
> 3. Dial accuracy
> 
> I have recently acquired an HQ-145a and have been using it as my main
> receiver for a while now. I did notice things like. Double Spotting and
> dial accuracy/alignment problems. I would like to know what its limits
> before I start further alignment.
> 
> I am also looking for an s-meter cover for it. if somebody has one please
> send me pricing so i can start saving up :)
> 
> regards
> fernan ve4feb
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL