Radio Shack 12-902 AM Extended Range Radio

Radio Shack 12-902 AM Extended Range Radio

Post by Neutrody » Mon, 05 Nov 2001 01:49:31

>Subject: Radio Shack 12-902 AM Extended Range Radio

>Date: 11/3/2001 12:30 AM Central Standard Time

>Does anyone know how this radio compares to the Superadio?  My wife got me
>one
>and it seems to work much better than my old clock radio it's replacing.  :)

>Also, it has a single***for an AM antenna, but an old AM Loop antenna I
>have has two connectors.  Can I just put both on the AM terminal, or do I
>need
>a different antenna?

>Thanks!
>-Richard

Hook one wire to the AM terminal and the other to ground, whertever you can
find one (battery "-" terminal, FM ant ground, etc.)
Neutrodyne
 
 
 

Radio Shack 12-902 AM Extended Range Radio

Post by Clifton T. Sharp Jr » Mon, 05 Nov 2001 08:22:16



> Does anyone know how this radio compares to the Superadio?  My wife got me one
> and it seems to work much better than my old clock radio it's replacing.  :)

I've been curious about that myself. I tried a store model (they let me
take it just out the front door) and it didn't seem all that sensitive,
but that wasn't a good test. Didn't want to buy one just to test it.

--
"I would have been happy to explain further, except you had by that
 point made it clear you would believe whatever you wanted to believe"

 
 
 

Radio Shack 12-902 AM Extended Range Radio

Post by radiok3 » Mon, 05 Nov 2001 13:33:14

Actually, I believe the model # is 12-903.

Anyway, I went through 2 samples in the past week.  Based on the 2 I
tried, I can tell you that the sensitivity on AM is really
disappointing...especially since they bill this as an Extended Range
radio.  Both of the units I bought had a severe drop off in gain at
about 1580 kHz.  The radio is simply deaf between 1580 and 1700.  You
have to crank the volume up to full to hear anything at all (and that
is not much) at those freqs.  Beyond that, the audio on AM left a lot
to be desired.  It was really tinny.  Keeping the trebel at min and
bass at max was about the only way to listen to it on AM.  I did a
side by side with my Superadio 2 and 3.  No comparison.  The Superadio
is the clear and overwhelming winner in that race.

I returned it today and exchanged it for the little analog shortwave
(DX-397) which is on clearance now for $30 and cash difference.  Nice
radio as far as cheapo analogs go.

It is of course possible that I got two lemons in a bad lot of 903's.
If anyone finds this radio to be a good performer, please post your
experience with it.

Russ


> >Subject: Radio Shack 12-902 AM Extended Range Radio

> >Date: 11/3/2001 12:30 AM Central Standard Time

> >Does anyone know how this radio compares to the Superadio?  My wife got me
> >one
> >and it seems to work much better than my old clock radio it's replacing.  :)

> >Also, it has a single***for an AM antenna, but an old AM Loop antenna I
> >have has two connectors.  Can I just put both on the AM terminal, or do I
> >need
> >a different antenna?

> >Thanks!
> >-Richard

> Hook one wire to the AM terminal and the other to ground, whertever you can
> find one (battery "-" terminal, FM ant ground, etc.)
> Neutrodyne

 
 
 

Radio Shack 12-902 AM Extended Range Radio

Post by <Do.. » Mon, 05 Nov 2001 23:00:08

I suggest putting 1 connector on the ant lug
and the other end of the loop to an earth lug or chassis***on the radio.

If you want to get clever take a 365 PF or so variable capacitor
( get one out of an old radio)
and wire that in your antenna circuit.
Put the return loop wire to that,  then wire the other side of the cap
to your earth lug or the chassis screw.

So you have a set up that is this .
You have your loop fixed to the 1st connector / the ant connector.
Your loop go out side does its loopy thing and comes back in the shack,
 Take the return end fix it to the cap then put a wire from the other side
of the cap
to the earth lug to complete the loop.

(Clear as mud!)

You can then tune your loop with the cap and peek signals
or null out interference to a degree.

NOW if you wanna be really clever take a length of uncovered cooper wire
and make a 20 turn coil (wind it round a pipe ) put this after the cap
and fix 1 end to the cap and the other to the ant.

Then make a jumper wire with  a crocodile / alligator clips on it
you can then peek up the ant by clipping the jumper along the coil
until you get the best S level also tuning the cap to peek sigs and or null
out unwanted noise!
If you want to you can put a cap at each side of the  coil,
make yourself a few jumpers and stick em here and there,
experimenting as you go! That's a very simple Antenna Tuning Unit

It's fun, as you will learn, also you will get better results than just a
loop.
Do it right and you might save the world!
All the best have fun! Bob
Next week BALUNS for the masses!

 
 
 

Radio Shack 12-902 AM Extended Range Radio

Post by Pete Gianakopoulo » Tue, 06 Nov 2001 14:59:26

I would be willing to bet that the radio is being aligned with the same
procedure as the 540 to 1600KHz unit, whereas the low end is being peaked at
600KHz, and the high end is peaked at 1400KHz.  The high end trimmers need
to be peaked at 1550KHz, with the third point tracking adjustment at
1050KHz.  That should flatten the response over the tuning range.  Ulrich
Rohde explains this concept pretty clearly in his book entitled
Communications Receivers: Principles and Design.
It is pretty much a survey book, with some good design examples.

Pete  KE9OA


Quote:> I suggest putting 1 connector on the ant lug
> and the other end of the loop to an earth lug or chassis***on the
radio.

> If you want to get clever take a 365 PF or so variable capacitor
> ( get one out of an old radio)
> and wire that in your antenna circuit.
> Put the return loop wire to that,  then wire the other side of the cap
> to your earth lug or the chassis screw.

> So you have a set up that is this .
> You have your loop fixed to the 1st connector / the ant connector.
> Your loop go out side does its loopy thing and comes back in the shack,
>  Take the return end fix it to the cap then put a wire from the other side
> of the cap
> to the earth lug to complete the loop.

> (Clear as mud!)

> You can then tune your loop with the cap and peek signals
> or null out interference to a degree.

> NOW if you wanna be really clever take a length of uncovered cooper wire
> and make a 20 turn coil (wind it round a pipe ) put this after the cap
> and fix 1 end to the cap and the other to the ant.

> Then make a jumper wire with  a crocodile / alligator clips on it
> you can then peek up the ant by clipping the jumper along the coil
> until you get the best S level also tuning the cap to peek sigs and or
null
> out unwanted noise!
> If you want to you can put a cap at each side of the  coil,
> make yourself a few jumpers and stick em here and there,
> experimenting as you go! That's a very simple Antenna Tuning Unit

> It's fun, as you will learn, also you will get better results than just a
> loop.
> Do it right and you might save the world!
> All the best have fun! Bob
> Next week BALUNS for the masses!