Yes, I did think of temperature concerns. The radio unit itself should
be kept at above freezing if my calculations are correct. However,
does the antenna need to be kept warm?

Owen Duffy wrote:
On Fri, 28 Jul 2006 22:29:51 GMT, Owen Duffy wrote:


sending an experimental balloon to over 100,000 ft. I have purchased
two 900MHz RF Aerocomm ConnexLink Radios. The radios have a power of
1000 m.a., which states it will transmit and receive up to 20 miles
line of sight. I do realize that this is probably under ideal

I did mean to comment on the temperature spec for the radio. The
temperature in the troposhere can be as low at -50 to -75 deg C, will
the radio get cold enough in transit to fail (eg battery failure,
condensation etc).

Owen
--

If the radio is the CL4790-1000 it is rated to -40C. For short term exposure to
cold, have you considered a small thermal blanket? It is drawing 5 watts from
the battery and power output is one watt. So, you have 4 watts of heat. Possibly
enough for a small thermal blanket.

Antenna should not require any heating element.



wrote:

Yes, I did think of temperature concerns. The radio unit itself should
be kept at above freezing if my calculations are correct. However,
does the antenna need to be kept warm?

Owen Duffy wrote:

On Fri, 28 Jul 2006 22:29:51 GMT, Owen Duffy wrote:



sending an experimental balloon to over 100,000 ft. I have purchased
two 900MHz RF Aerocomm ConnexLink Radios. The radios have a power of
1000 m.a., which states it will transmit and receive up to 20 miles
line of sight. I do realize that this is probably under ideal

I did mean to comment on the temperature spec for the radio. The
temperature in the troposhere can be as low at -50 to -75 deg C, will
the radio get cold enough in transit to fail (eg battery failure,
condensation etc).

Owen
--

wrote:
Yes, I did think of temperature concerns. The radio unit itself should
be kept at above freezing if my calculations are correct. However,
does the antenna need to be kept warm?

Hi Brett

In most cases, the transmitter will be in an enclosure. I'm assuming
that there will be an experiment package. Many who do this sort of thing
will make the enclosure out of Styrofoam. Some actually use styro picnic
coolers. For typical flight durations, the inefficiencies of the
electronics equipment on board the payload (read waste heat) will make
up for the nasty temps outside. I've seen some cases where there has
actually been a temperature rise. The criteria is a well sealed
insulating box.

And no, the antenna itself does not need to be warm. Just seal off the
exit port to keep internal heat from leaking out.

Your watt should be sufficient power. At 100 kilofeet, you will reach
more that you likely want to reach! I've seen propagation maps that show
a single balloon repeater at these heights covering 1/3rd of the US.



- 73 de Mike KB3EIA -