[Hallicrafters] R45/ARR-7 Receiver by Hallicrafters

Mon Mar 5 11:37:47 EST 2018

Hello Chuck & Joe,
Many thanks for your replies. 
I downloaded a copy of the manual from BAMA and have read and re-read para 5-24.
Its true what you said Chuck:  it appears that you need to vary the sig gen frequency up and down from 455 to find the exact crystal frequency and tune the IFs accordingly so thank you for reminding me of that.
Joe, thanks for finding that little gem of information about bypassing the re-radiation suppressor stage.  I’ll give that a try and see what happens.
I really cant see why they found it necessary to use this as depending on which band you are on, there is one or two RF stages in front of the mixer.

There are some videos on youtube where an ARR-7 radio is being demonstrated; there is a background liveliness noise which my set doesn’t have.
This is why I suspect low gain somewhere – possibly in more stages than just one or just all of them!
There was +18volts on the grid pin of the 6V6 with no heater voltage applied so I replaced THAT capacitor (C10) to avoid problems.
I’ll hook up an output meter and see what checks I can do on the audio stages as well.
On the BAMA site, I found a document about mods. One of the mods is to fit a proper output transformer which could be a good idea.
I didn’t find any descriptions that went with the mods so in Fig 1, I dont know what the white wire with blue tracer is all about!

73, Alf

From: Joe Connor 
Sent: Monday, March 05, 2018 2:31 PM
To: Joe Connor ; Chuck McGregor ; Alf Fisher 
Cc: Hallicrafters at mailman.qth.net 
Subject: Re: [Hallicrafters] R45/ARR-7 Receiver by Hallicrafters

I found this in the archives about bypassing the re-radiation suppressor. See if it helps.

 From what I've read, it's a good idea to bypass V-12 (6AB7), the radiation suppression tube. How do I go about bypassing it?

Just stick a .01uF capacitor across pins 4 and 8 of the tube socket, 
Joe.  I used a couple of pins from an old tube socket so it just plugs 
in.  No soldering required.

Joe Connor

On Sunday, March 4, 2018 7:02 PM, Joe Connor via Hallicrafters <hallicrafters at mailman.qth.net> wrote:

Isn't there a trick to bypass the 6AB7 re-radiation suppressor (V-12?) to improve sensitivity? I'm going by memory here.
Joe Connor 

    On Sunday, March 4, 2018 6:40 PM, Chuck McGregor <cbmcgr at gmail.com> wrote:

Alf-
The R-45, like the SX-28 has a crystal filter. The IF should be aligned to
the actual frequency of the crystal in the set. This may be one or two kc
away from exactly 455.

The data in the military manual  AN16-30ARR7-2 is all that I have seen. It
is available at
http://bama.edebris.com/manuals/hallicra/r45arr7/r45mil

73
Chuck K7MCG

On Sat, Mar 3, 2018 at 2:45 PM, Alf Fisher <alffisher2 at gmail.com> wrote:

> Hi everyone,
>
> I recently acquired one of these sets which is a reduced spec version of a
> SX-28 in an airborne ATR case and today I’ve been giving it a check over.
>
> The set seems somewhat “deaf” and I wonder if its bad capacitors or if
> they were prone to IF transformers going low Q after being stored in a damp
> environment although it was MFP treated.
>
> I checked what frequency they were tuned to and instead of 455 kc they are
> around 448 kc and the cores one one side are screwed almost fully in and
> the other side are a long way out.  Is this normal?
>
> Is there a reason for them being tuned to a lower frequency or has it been
> tweaked by someone with a sig gen that’s not very accurate and they should
> be spot on 455 kc.
>
> I was also hoping to find some data on the expected stage gains and
> sensitivities in the manual so if anyone can help me out with advice, that
> would be great.
>
> 73,
> Alf, G3WSD
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