[HBR] Beam deflection mixers

[Shoppa, Tim]

The beam deflection mixer designs that I find most appealing are on the simplistic end of the spectrum and the Goodman (W1DX) band-imaging designs really are appealing.

An 80M/40M band imaging receiver has the IF right were you describe, at 1.7 MHz or so.

The Goodman design that appeals to me the most is the Miser's Dream: May 65 QST or on the web here: http://mysite.verizon.net/dpnewkirk/ej/misers_dream/ But I would be tempted to simplify it even more to stop it from turning into a neverending project :-).

I think it could be simplified even further, if I were to do one today I'm sure I'd skip the double conversion aspect, and just have the IF at 5-9 MHz ballpark with some homebrew crystal filters depending on which two bands I was going to cover. I'm thinking a single IF amp stage would be about right. And I'd skip the RF Amp (aka "Q multiplier") at the front end instead depending on a double-tuned or triple-tuned bandpass for image rejection, and make sure the beam deflection tube in the front end had balanced LO at the deflection plates. Maybe a beam deflection tube used for the product detector too.

I don't have any 7360's but several years ago I stocked up on 6AR8's to try to realize this ambition of mine. I did brew up a simple converter using a 6AR8 but it was just two tubes... I'd have to add another 3 or 4 tubes to make a CW or SSB receiver.

I think it's W1VD's page (or maybe somewhere else) that the importance of matching the antenna to the input filters was brought up. Most ham receivers of the time had a lot of RF gain and poor matches to the antenna were hardly noticed. The Squires-Saunders design really was aimed at having the "right amount" of gain rather than an excess of gain.

Tim N3QE

-----Original Message-----
From: hbr-bounces at mailman.qth.net [mailto:hbr-bounces at mailman.qth.net] On Behalf Of Peter Bertini
Sent: Monday, September 12, 2011 1:30 PM
To: HBR Receiver List
Subject: Re: [HBR] Beam deflection mixers

Those mixers are a good way to pick up extra rejection of IF signal blowby,
especially
for sets using 1st IF frequencies in the new
expanded AM band.

Pete
On Mon, Sep 12, 2011 at 6:41 AM, Shoppa, Tim <tshoppa at wmata.com> wrote:

> WV1D publishes some Squires-Sanders SS-1R test results:
>
> http://www.w1vd.com/SS-1R.html
>
> When used in single conversion, it beats the pants off everything else out
> there at the time in terms of dynamic range. (Well, except a R-390.)
>
> But in the 60's specsmanship was all about sensitivity (uV then... MDS
> today.). Even today we see folks bragging about their receiver's ability to
> pick up 0.03uV on the bench... and somehow ignoring that the atmospheric
> noise on the lower bands is 100x stronger :-).
>
> Of your two beam deflection mixer schemes, it seems to me too that method
> (a) would offer highest linearity. But method (b) was surprisngly popular.
> The real test would be a comparison via measurements.
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