[Hammarlund] IF bandwidths?

[peter markavage]

If your going to use the 1496 to drive the panadapter, you don't want a
balanced modulator. Figure 29 (double balanced mixer) is what you should
be using. You would still need an oscillator source for the 1496 and the
1496 output is tuned to the input frequency of the panadapter(21.4 MHz).
Generally a panadapter is connected to the output of the mixer (the plate
of tube rigs through a small (5, 10 pf coupling cap) of the receiver
before it goes into the first IF amplifier. Connecting after the first IF
tends to make the panadapter screens readings bogus and plus you also
have to contend with IF stage gain and noise, etc. 

I wouldn't worry USB or LSB. If you're connecting to a mixer input of a
455KHz IF in the receiver and you know the output of the homebrew mixer
has to be 21.4 MHz, the local oscillator input to the homebrew mixer
should either 21.855 or 20.945 depending on which way you want to mix it.
Your bandwidth, +/- whatever, is mainly dependant on the panadapter sweep
circuitry. You would also want a stable local oscillator input to the
homebrew mixer so crystal controlled probably would be the best choice.

Pete, wa2cwa


On Thu, 13 Oct 2005 02:16:43 +0000 "Eugene Hertz" <ehertz at tcaf.org>
writes:
> I found a very interesting circuit that I will persue.  It is figure 
> 25 on page 10 in the MC1496 data sheet which can be found here: 
> http://www.onsemi.com/pub/Collateral/MC1496-D.PDF
>  
> I just have to figure out how to supress one sideband, and I think I 
> might be onto something!
> 
> I've been trying to figure out some details, it seems like if I plan 
> on a 100khz bandwidth centered on 455khz (+/- 50khz), I would have a 
> choice of LO's depending on if I want to use the LSB or USB image. 
> Please correct me here because I am first just learning about this 
> stuff. The LO options would be 21.855 and use the LSB or 20.945 and 
> use the USB. But what I think I figured out that my only option is 
> 21.855 and using lsb, otherwise the unwanted image will show up in 
> the bandpass. Something like that. 
> 
> Anyway, getting back to hammarlunds. I also realized that these 
> radios have two conversions, does anyone know if the IF bandwidth is 
> wider after 3.955 or 455 when two conversion stages are used?
> 
> Eugene
>  
> 
> 
> >-----Original Message-----
> >From: peter markavage [mailto:manualman at juno.com]
> >Sent: Wednesday, October 12, 2005 04:09 PM
> >To: hammarlund at mailman.qth.net
> >Subject: Re: [Hammarlund] IF bandwidths?
> >
> >Why not just build a simple 1 tube (or solid-state) mixer. 21.400 - 
> (1st 
> >IF Frequency) = Mixer Frequency 
> >Pete, wa2cwa 
> > 
> >On Wed, 12 Oct 2005 20:53:51 +0000 "Eugene Hertz" <ehertz at tcaf.org> 
> 
> >writes: 
> >> Hello all, 
> >> 
> >> I am undertaking a project (probably foolishly) to adapt a 
> 21.4mhz 
> >> panadapter for use with various hammarlunds, specifically sp600, 
> 
> >> hq140x, hq129x. The idea is to use a balanced modulator, and no, 
> I 
> >> havent figured it all out yet (and it may not even be possible). 
> 
> >> 
> >> In trying to figure it all out, I was wondering if anyone has 
> ever 
> >> made any IF bandwidth measurements of these receivers at their 
> >> widest points in the circuits, before filters. 
> >> 
> >> Thanks 
> >> Eugene