[HBR] IF cans for HBR

Sat Sep 20 14:41:15 EDT 2008

Actually, I have used I.F. regeneration at 1650 Kc (and at 1415 & 730 kc, in Command sets)  and it definitely does yield a useful and effective improvement in selectivity. The disadvantage of a simple I.F. regen.system is that it's  fix-tuned  to the I.F,  somewhat 'touchy' & requires manual adjustment of  reciever I.F. gain to prevent oscillation and overload of succeeding stages.  
The Hallicrafters SX-140 "Novice" reciever  used this system (at 1650kc) to  give a slick & simple boost to it's capabilities. A separate, tunable Q-multiplier circuit would be more flexible and effective, as one could start with a really Hi-Q inductor, and much        less likely to cause gain distribution issues. I've never personally tried to use an inverting amp stage with an I.F. Q-mult. higher than 500kc, but an RSGB handbook (fourth edition, I think), showed a reciever circuit by  G3PDM which used Q multiplier with a notching/inverting stage at 1620 kc, so the idea must have some merit. This reciever also uses a 7360 mixer with no R.F. stage, balanced injection to the deflector plates from a hybrid pll circuit, an I.F. with three individually adjustable half lattice crystal filter sections distributed between the stages and a self excited, crystal controlled, balanced, 7360 product detector, with the I.F.
signal applied to the deflection plates. A very interesting reciever circuit indeed!
In my version of the Crosby HBR, I would not hesitate to use a first I.F. Q-Mult, even if only for the peaking effect, and a separate Q-mult. or a tee-notch at 85 or 100 kc as well.
DSR

From: Peter Bertini <radioconnection at gmail.com>
Subject: Re: [HBR] IF cans for HBR
To: wb8rav at yahoo.com, "HBR Receiver List" <hbr at mailman.qth.net>
Date: Friday, September 19, 2008, 7:48 PM

Hi DSR..

Has anyone tried using a Q-Multiplier at the first IF?  And if so, how
effective was it at 1600kc?  I had considered the idea, but thought it
might be redundant having two Q-Multipliers in the same radio...  One
the other hand, that's one way to sharpen the first IF BW as you
noted, and I wonder if the Notch Filter function would be sharp
enough.  I certainly have enough front panel space for additional
controls. A simple half-lattice filter would be nice, if a pair of
crystals could be had for less than a king's ransom. I suspect they
could even be fitted inside of one of the ARC-5 IFTs to save chassis
space.

I was planning on adding an extra ARC-5 IFT (two in cascade) for the
1st IF, but with a Q-Multiplier that might not be needed?

Strong mixing stages would be nice, but I still think the harmonic
mixing scheme limits the choices for what will work in the first
mixer, and its performance, on those bands where the second harmonic
is used.  I'm tempted to forgo coverage above 10 or 14mc for the sake
of using a balanced beam tube...

Pete

On Fri, Sep 19, 2008 at 5:50 PM, David Richards <wb8rav at yahoo.com> wrote:
>  Four tuned circuits operating at 1600-1700kc  should ensure that only a
reasonably small slice of frequencies could cause problems before the highly
selective elements at the lower IF come into play. Use of strong mixing stages
and holding  pre-selectivity gain to 'just enough' to comfortably
compensate for losses should eliminate the need for a  crystal filter at the
first IF.  If this caveat is observed, the '59 approach will work very well.
For tough, 'close-in' band-crowding conditions, a peaking Q-multiplier
constructed to operate at the first I.F. can be very helpful; especially on cw,
and is a much simpler and less restrictive
> approach. DSR
>
> --- On Fri, 9/19/08, Peter Bertini <radioconnection at gmail.com>
wrote:
>
> From: Peter Bertini <radioconnection at gmail.com>
> Subject: Re: [HBR] IF cans for HBR
> To: "HBR Receiver List" <hbr at mailman.qth.net>
> Date: Friday, September 19, 2008, 12:46 PM
>
> Absolutely!
>
> The W6TC receivers are based on technology that was state of the art in
1959.
>
> One of the points is having the bulk of the selectivity after three stages
with
> significant gain: RF amplifier, and the two mixers!
>
> The HR-10 offers some excellent possibilities,
> in my humble opinion, to bring the HBR's performance up a notch or
two.
>
> I'd use the half-lattice crystal filter section from the
> HR-10 and  use in the HBR circuit.  It is a modest filter, but
> it will give the second mixer greater protection to strong signals to
> out of passband
> signals than is offered by LC filtering alone.
>
> The 85kc IF will still provide the bulk of the selectivity and
> receiver IF passband
> shape factor, and the 1600kc IF transformer will provide the needed
> filtering for
> any spurious responses in the half-lattice filter stop band.
>
> I' ve been looking for a junker HR-10 to raid the filter crystals
> from!  If you don't
> use them, I'd be interested in buying them :)
>
> One other possibly usable part is the tuning cap, I'm not sure what
the
> range is, but it might be usable if removing a plate or two will bring the
> minimum and maximum capacity close to that of the Millen part used in the
> original HBR.  Regardless, most subs are going to require some
> needed rework of the original coils.
>
> Pete
>
> On Fri, Sep 19, 2008 at 4:03 AM, Clarence Peckham
> <cpeckham at mindspring.com> wrote:
>> Good morning,
>>
>> I am new to the list and have question. Is anyone using the parts form
a
>> heath HR10 to make an HBE? I noticed that the IF frequency is almost
the
>> same so a lot of the parts should be usable right?
>>
>> Thanks,
>>
>> Clarence, NT7V
>> ************************************
>> Visit the HBR Receiver Web Site with over 100 pictures of receivers
and
>> construction notes...... via http://www.qsl.net/k5bcq/ there is also a
>> mirror (faster response)at http://k5bcq.edebris.com/
>>
>>
>> Retrieve reflector archived data via
>> http://mailman.qth.net/mailman/listinfo/hbr
>>
>>
> ************************************
> Visit the HBR Receiver Web Site with over 100 pictures of receivers and
> construction notes...... via http://www.qsl.net/k5bcq/
> there is also a mirror (faster response)at http://k5bcq.edebris.com/
>
>
> Retrieve reflector archived data via
> http://mailman.qth.net/mailman/listinfo/hbr
>
>
>
>
>
> ************************************
> Visit the HBR Receiver Web Site with over 100 pictures of receivers and
> construction notes...... via http://www.qsl.net/k5bcq/
> there is also a mirror (faster response)at http://k5bcq.edebris.com/
>
>
> Retrieve reflector archived data via
http://mailman.qth.net/mailman/listinfo/hbr
>
>