[R-390] Below 500khz?

Mon, 19 May 2003 16:42:49 -0400

At 06:27 PM 5/16/03 -0500, Robert M. Bratcher Jr. wrote:
>Is there a way to make an 390a receive below 500khz all by itself?

Yes. An article in Hollow State News   detailed the technique, but 
basically it is this:

Disconnect your regular antenna (or pull out the RF Amplifier tube) and 
attach it or your LF antenna to test point E208 on the RF deck.

>Is it as sensitive as above 500?

No.

>What happens when you hit 500? It sounds like the audio gets muted but I'm 
>not sure....

With the receiver in normal configuration, the front end tuned circuits do 
not respond well below 500kc.. all signals get attenuated compared to above 
that frequency.

>If it's not possible then I'll build a converter that puts 0 to 500 
>between 4 & 4.5mhz.

A number of converters are available to do the job, Heath made one.  Look 
below for reference to at least one converter article.

 From my collected notes here are a couple of messages from the past:

>Subject: [R-390] Operating the R390 from 0 to .5
>To: [email protected]
>From: "Roger L Ruszkowski" <[email protected]>
>Date: Fri, 25 Aug 2000 15:54:25 -0700
>Sender: [email protected]
>Reply-To: "Roger L Ruszkowski" <[email protected]>
>
>
>Roger,
>I remember that you commented once before that you'd seen the R390A's 0-.5
>band shifted down. But practically, what do you do? I presume that you
>tune the tank circuits at something like 100kHz and 400kHz with the
>appropriate inductor and trimmer.
>Then what kind of sensitivity do you get across the band? I do not know
>I have never measured it. I agree with your next comment. I presume not too
>good as Collins has a whole radio
>(R389?) that tunes that 0-.5mHz range in about 7 bands.
>Can you provide specifics on how to get the 390A to tune below 500 kHz?
>Tom, W4PG
>Tom,
>Watch the cams move as you tune from .5 to 1 and then the 1 - 2 cam as you
>tune from 1 - 2. The .5 to 1 cam will be high at 1 bottom out at .5 and
>then
>go off high again to nowhere as you tune on down to zero.
>There is some low point where the cap and slug just will not resonate any
>more.
>this is the low end of the thing. Or you start loosing sensitivity real
>quick.
>Pick a top range point (700KHz). Run the dial over to there and get a good
>cal zero. Loosen the .5 to 1 clamp and move the cam so this is the high
>point.
>and clamp it back down. As you tune over 700 you go over the top of the cam
>and
>loose tracking. at 200 you meet the bottom of the cam and loose tracking.
>Now start to tweak the slug at 250 and the cap at 650. If you run out of
>slug range before you peak out, then move the cam over a bit to get back in
>range.
>This will reduce the range to less than 500. Play with this and then try to
>go
>lower in frequency if you want.
>You do not have to keep the band to full width. you can trim the cap and
>slugs for some points less on all bands. I have seen a few receivers where
>the 4 to 7+000 was tweaked for 7 to 7.5. And where 2 - 3+000 tweaked for 3
>3.5
>for ham use.
>I do not know what is under .5 there is a band down there of interest to
>hams.
>It was just some thing we did to a receiver once upon a time because it
>could be done
>and we were wondering what we could hear.
>Roger.
>Subject: [R-390] Operating the R390 from 0 to .5
>To: [email protected]
>From: "Roger L Ruszkowski" <[email protected]>
>Date: Fri, 25 Aug 2000 15:54:25 -0700
>Sender: [email protected]
>Reply-To: "Roger L Ruszkowski" <[email protected]>
>
>
>Roger,
>I remember that you commented once before that you'd seen the R390A's 0-.5
>band shifted down. But practically, what do you do? I presume that you
>tune the tank circuits at something like 100kHz and 400kHz with the
>appropriate inductor and trimmer.
>Then what kind of sensitivity do you get across the band? I do not know
>I have never measured it. I agree with your next comment. I presume not too
>good as Collins has a whole radio
>(R389?) that tunes that 0-.5mHz range in about 7 bands.
>Can you provide specifics on how to get the 390A to tune below 500 kHz?
>Tom, W4PG
>Tom,
>Watch the cams move as you tune from .5 to 1 and then the 1 - 2 cam as you
>tune from 1 - 2. The .5 to 1 cam will be high at 1 bottom out at .5 and
>then
>go off high again to nowhere as you tune on down to zero.
>There is some low point where the cap and slug just will not resonate any
>more.
>this is the low end of the thing. Or you start loosing sensitivity real
>quick.
>Pick a top range point (700KHz). Run the dial over to there and get a good
>cal zero. Loosen the .5 to 1 clamp and move the cam so this is the high
>point.
>and clamp it back down. As you tune over 700 you go over the top of the cam
>and
>loose tracking. at 200 you meet the bottom of the cam and loose tracking.
>Now start to tweak the slug at 250 and the cap at 650. If you run out of
>slug range before you peak out, then move the cam over a bit to get back in
>range.
>This will reduce the range to less than 500. Play with this and then try to
>go
>lower in frequency if you want.
>You do not have to keep the band to full width. you can trim the cap and
>slugs for some points less on all bands. I have seen a few receivers where
>the 4 to 7+000 was tweaked for 7 to 7.5. And where 2 - 3+000 tweaked for 3
>3.5
>for ham use.
>I do not know what is under .5 there is a band down there of interest to
>hams.
>It was just some thing we did to a receiver once upon a time because it
>could be done
>and we were wondering what we could hear.
>Roger.

>From: "Steve Goode" <[email protected]>
>To: "Bruce" <[email protected]>, <[email protected]>
>Subject: Re: [R-390] LW reception on R390A
>
>I would also be interested in any mod for below 500 kHz.  I am hoping to
>build the LF converter in the April QST.
>
>Steve, K9NG
>
>----- Original Message -----
>From: "Bruce" <[email protected]>
>To: <[email protected]>
>Sent: Thursday, May 02, 2002 11:50 AM
>Subject: [R-390] LW reception on R390A
>
>
> > Hi Folks,
> >
> > Long time listener, first time caller, hi.
> > I seem to recall reading a post a long time back about a simple mod to
> > enable the '390A to hear freq's below 500kc's. Could someone explain the
> > mod, or direct me to the proper resource?
> >
> > Much obliged.
> >
> > 73,
> > Bruce Bacon - KE6GLS
> > Boise County, ID
>
>From: Helmut Usbeck <[email protected]>
>To: <[email protected]>, <[email protected]>
>Subject: RE: [R-390] LW reception on R390A
>
>Disconnect your regular antenna and attach it or your LF antenna to
>test point E208 on the RF deck.  E208 is to the lower right of V201,
>the RF amp.  The setup works pretty good.  If you have or can build a
>LF antenna tuner it's much better.  Any of the available published
>plans of converters will work.
>
>Helm.  WB2ADT

>To: [email protected]
>From: Roy Morgan <[email protected]>
>Subject: RE: [R-390] LW reception on R390A
>Sender: [email protected]
>Date: Thu, 02 May 2002 17:14:43 -0400
>
>At 03:50 PM 5/2/02 -0500, Barry(III) - N4BUQ wrote:
>Well, with a 455kc IF, you already have a "receiver" that will "hear" 
>below 500kc.  :)
>
>
>Yup.. but listening to just 455 kc may be boring.
>
>A Hollow State News article that may relate to this topic is:
>
>Issue No 2, page 3. "Longwave Conversion"  This may be the article I 
>remember, or perhaps there was an Electric Radio article.

- Roy Morgan
National Institute of Standards and Technology
100 Bureau Drive, Stop 8970
Gaithersburg  MD 20899-8970
Voice: 301-975-3254  Fax: 301-948-6213
E-mail:  [email protected] --