Lostgallifreyan wrote:
Does anyone know what the Sangean ATS-909's external antenna input impedance
is?
SNIP

What I really want to know is whether the ATS-909 will work ok with a
long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if
that would cause more bother than connecting a wire directly to it and
putting up with local noise picked up from nearby buildings.

There's a 1K0 pot across the input which is used as a cheap and cheerful
RF gain control. So i'd assume about 1K. You wouldn't have a problem
with the wire attached direct, but you'll get lots of front end
intermod, as it's wide open - just a low pass filter (presumably 30MHz
cut off)before the RF amp. A bit of preselection is pretty necessary for
an external wire of any size.

Gaius wrote in
:

Lostgallifreyan wrote:
Does anyone know what the Sangean ATS-909's external antenna input
impedance is?
SNIP

What I really want to know is whether the ATS-909 will work ok with a
long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or
if that would cause more bother than connecting a wire directly to it
and putting up with local noise picked up from nearby buildings.

There's a 1K0 pot across the input which is used as a cheap and cheerful
RF gain control. So i'd assume about 1K. You wouldn't have a problem
with the wire attached direct, but you'll get lots of front end
intermod, as it's wide open - just a low pass filter (presumably 30MHz
cut off)before the RF amp. A bit of preselection is pretty necessary for
an external wire of any size.



Front end intermod? Do you mean pickup from local active gain stages or other
RF subcircuits in the receiver being picked back up by the wire antenna and
makign sum/difference signals or similar effects?

Also, I see that pot now, (and noticed that it also affects the telescopic
inbuilt antenna's pickup on SW (not FM as far as I know)), but I also see a
lot of other parts associated with that part of the circuit. I don't know
enough to be sure but it seems they might complicate the picture. If not, I
don't know why the impedance seems to be a mystery. If it were well
established I know my searches would found it so in triplicate by now...

Lostgallifreyan wrote:
Gaius wrote in
:

Lostgallifreyan wrote:

Also, I see that pot now, (and noticed that it also affects the telescopic
inbuilt antenna's pickup on SW (not FM as far as I know)), but I also see a
lot of other parts associated with that part of the circuit. I don't know
enough to be sure but it seems they might complicate the picture. If not, I
don't know why the impedance seems to be a mystery. If it were well
established I know my searches would found it so in triplicate by now...

I've just found a schematic JPG - 475Kb. It claims to be a "RK777", but
I think that's one of the 909's aliases. I can send it - mail me at john
at aultmore dot net.

Gaius wrote in
:

Lostgallifreyan wrote:
Gaius wrote in
:

Lostgallifreyan wrote:

Also, I see that pot now, (and noticed that it also affects the
telescopic inbuilt antenna's pickup on SW (not FM as far as I know)),
but I also see a lot of other parts associated with that part of the
circuit. I don't know enough to be sure but it seems they might
complicate the picture. If not, I don't know why the impedance seems to
be a mystery. If it were well established I know my searches would
found it so in triplicate by now...

I've just found a schematic JPG - 475Kb. It claims to be a "RK777", but
I think that's one of the 909's aliases. I can send it - mail me at john
at aultmore dot net.


Thanks, but I'm ok, I got a schematic.. It just appears that those links
became forbidden access in the week or so since I found them. Might even be a
local error, thogh as I no longer do HTML or User-Agent filtering or similar
things I can't see what the cause might be.