[HBR] HBR-16 and LWM-3

Thu Mar 17 22:56:24 EDT 2016

Hi Lorne,  Good to hear from you. Right now I have to get a bunch of kits mailed out of here and get some Do Rags lined up with logos for the car group whose leader is undergoing Chemo....so it will be a few days. 73 Kees K5BCQ 

---------- Original Message ----------
From: "Lorne Barber" <bear57 at telus.net>
To: "'HBR Receiver List'" <hbr at mailman.qth.net>
Subject: Re: [HBR] HBR-16 and LWM-3
Date: Thu, 17 Mar 2016 19:49:00 -0700

Hi Kees, I am interested in the LWM 3. Always regret letting mine go.
Not sure I can afford the shipping these days.
I still have the (2)X 6146 homebrew amp that I built for it.
Tnx es 73
Lorne
VE7BOX

-----Original Message-----
From: HBR [mailto:hbr-bounces at mailman.qth.net] On Behalf Of Kees & Sandy
Sent: March-17-16 3:22 PM
To: hbr at mailman.qth.net
Subject: [HBR] HBR-16 and LWM-3

I think I'll move my HBR-16 receivers and my LWM-3 Transceiver on to new
homes ......other things are taking up my time and money. I'll keep the
HBR-12 and the HBR-13C. Pictures of the units are on the HBR website. 73
Kees K5BCQ

---------- Original Message ----------
From: Walt Hutchens <waltah at earthlink.net>
To: HBR Receiver List <hbr at mailman.qth.net>
Subject: Re: [HBR] HB-65 or HB-67 experience?
Date: Sun, 4 Jan 2015 13:57:11 -0500

Brian said:

> Anybody have any experience with either the HB-65 or HB-67 from the 
> 1966 and
> 1967 ARRL handbooks? Inquiring minds, and all that (;->).

No experience, but -- this isn't going to surprise anyone -- an opinion. As
a way to use a mechanical filter that you have and want to use this is good;
otherwise it's a mixed bag.

The problem in HF receivers is NOT low noise or hearing weak signals.
At least up to 20M the problem is rejecting the vast amount of garbage found
in and near the ham bands. The mechanical filter solves part of this problem
-- near channel interference -- but unless used with a great deal of
selectivity ahead of the filter, it does not solve the problem of images --
signals coming in on the other side of the LO frequency. That's because the
frequency is too low for a 1st IF.

A mechanical filter could work well at the start of a second IF, following a
1st IF of 1.6 Mcs or more. However the design up to the mechanical filter
would have to keep signals small because these filters don't handle large
signals well.

One could adapt the W6TC designs to use a 455kcs 2nd IF instead of the
85 or 100 kcs frequencies that are standard. Then use a 455kcs mechanical
filter after the 2nd mixer. That way you've got those high Q front end coils
lopping off the image on the lower bands where it'll be most troublesome.  

The HB-67 design (and relatives -- this design appeared at least
1965-69 in various flavors) could have been improved by the use of very high
Q front end coils a la W6TC, but since it's bandswitching and predates the
common use of toroids, not so.

I would probably also go with an RF stage run at close to unity gain in
order to simplify the coupling between the coils and allow AGC ahead of the
filter. The 6EH7 would be ideal for this. Of course that does complicate the
design.

For use right behind the 1st mixer CRYSTAL filters at higher frequencies are
an ideal choice. The Heath HR-10B filter -- two 1680kcs crystals in a
half-lattice arrangement -- is simple and works well.

These filters don't handle super-large signals either -- the crystals can
fracture, as found in some of the HR-10s out there, probably due to the
owner transmitting with the antenna still hooked to the receiver. But as far
as normal signals are concerned they're good and being located at the 1st
mixer makes it easier to keep signal amplitudes down. Up to the point of
fracture I don't think non-linear effects are a problem.

In fact, crystal filters and 'mechanical' filters are both mechanical
filters. The ones called 'mechanical' couple electrical signals to
mechanical resonators by magnetostriction while the crystal filters do it
via the piezoelectric effect, but in both cases you're using mechanical
vibration of a solid as a tuned circuit analog.

An additional minor issue with the HB-67 design is that it 'uses' a beam
deflection mixer basically as a high gain pentode mixer. To get the
advantage of balanced mixing (so that the input signal is canceled at the
output) it would need a balanced output circuit, meaning some sort of
coupling transformer ahead of the mechanical filter -- or a filter
specifically designed for balanced input.

Walt
KJ4KV

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