Attenuators for Direction Finding???
 

Where can I buy some attenuators to attenuate signals while Dfing?

Any good info or sources of info on the subject?

I'm going to try to do it with a HT and its S-meter.

On Sat, 20 Mar 2004 18:57:14 -0800, thatcher wrote:

Where can I buy some attenuators to attenuate signals while Dfing?

Any good info or sources of info on the subject?

I'm going to try to do it with a HT and its S-meter.

Hi Thatcher,

The S-meter on most FM handhelds are miserable poor indicators,
basically useful only as "busy" indicators.

Connect your sniffer antenna to a detector circuit feeding a good
digital voltmeter, and put a 300 Ohm variable resistor ahead of the
detector. The "good" digital voltmeter doesn't even have to be that
good.

73's
Richard Clark, KB7QHC

"thatcher" wrote in message
...
Where can I buy some attenuators to attenuate signals while Dfing?

Any good info or sources of info on the subject?

I'm going to try to do it with a HT and its S-meter.

You can get a "VCR attenuator" at radio shack for $6 or so.
It's not a lab quality device, but it's quite servicable.

One other thing to be aware of, most HTs cases are rather transparent, so
attenuation becomes ineffective pretty quickly, and the directional pattern
dissolves, as your signal level from the antenna approaches what's leaking
through the case and shielding of the HT.

If you are close enough to NEED an attenuator then the best one is your
antenna!

Remove it!!

DD

thatcher wrote:
Where can I buy some attenuators to attenuate signals while Dfing?

Any good info or sources of info on the subject?

I'm going to try to do it with a HT and its S-meter.

If really close, you could use your body as an attenuator. Hold the HT close
and rotate yourself, looking for a null. The signal will be at your back. On
attenuators, make them. The ARRL hand book has charts for both pi and t
types.

Phil, KB2HQ

"Dave Shrader" wrote in message
news:Jxn7c.55130$_w.877825@attbi_s53...
If you are close enough to NEED an attenuator then the best one is your
antenna!

Remove it!!

DD

thatcher wrote:
Where can I buy some attenuators to attenuate signals while Dfing?

Any good info or sources of info on the subject?

I'm going to try to do it with a HT and its S-meter.

What is the matter with the receiver gain control?

If you must use an external attenuator it need not be matched. A simple
variable 100-ohm pot with a knob on it is good enough for direction finding.

On Mon, 22 Mar 2004 12:22:53 +0000 (UTC), "Reg Edwards"
wrote:
What is the matter with the receiver gain control?

Because most are not true gain controls, but instead are squelch level
controls (quite obvious if the S-meter changes with the position of
the so-called RF Gain setting). When doing this kind of hunting by
decimation of signal, it is the interfering signal to co-channel
signal ratio that matters. As you close in on the interfering source,
that ratio changes, but you still need the sensitivity to reckon a
bearing while at the same time attenuating both. In such cases the
front end levels are expendable (through an external attenuator), the
sensitivity is not (through the internal "gain" control).

73's
Richard Clark, KB7QHC