On May 30, 12:50 pm, scooterspal wrote:
OK. I have tested the frequency and found it to be 75.489Mhz. Should
have done this first, sorry for the confusion. Comtek did make systems
that operated betweeh 72 and 76Mhz. This is one of those.

That said, where do I stand antenna wise?

Thanks!

Depending on how large a distance you want it to cover, you may get by
with a considerably shorter antenna than the 48 inch recommended
size. But you also didn't say, that I could see, that there was a
problem using a 48" piece of wire. Obviously it's not too critical
since in use the mic cable can be bent in all sorts of different
shapes and it still operates. In other words, try to not make this
more difficult than it needs to be. If you need the mechanical
antenna to be shorter than 48 inches, just wind that length of wire in
a spiral, spaced out as much as you can accommodate. Try that and see
how it works. Easy enough? If you need higher performance, that's
possible, but in general very short antennas won't be as efficient as
straight antennas long enough to be self-resonant at the operating
frequency. If you need good performance from a short antenna, get a
system that operates at a higher frequency.

Cheers,
Tom

On Fri, 30 May 2008 11:36:25 -0400, scooterspal
wrote:

Hello and thanks for ahy help you can provide.

I have a small assisted hearing type transmitter that normally uses the
shield of the mic cable for the antenna. I need to change to a fixed
antenna for a particular application where there is no mic cable to
extend out.

The manufacturer says the antenna wire for this 651.85Mhz unit should be
48" long.

Can anyone tell me what that would equal in a rubber ducky antenna?

Thanks.

Which model do you have?
http://www.comtek.com/sitemap.html
choose the model, and the device frequency range will be listed. They
only show three frequency ranges, 216-217 Mhz, 72-76 MHz, and 76-78
MHz. They also have several options for external antennas, but I
think these are primarily for the base transmitters.

As mentioned in an earlier reply, if you build your own antenna, the
device _may_ become compliant.


--
73 for now
Buck, N4PGW

www.lumpuckeroo.com

"Small - broadband - efficient: pick any two."