CM 25dB Preamp vs GE 22dB Amp

I have a CM 4228 in my attic going through a cheap 10dB amp and usually
pick up most of the signals in my area, but occasionally have drop outs.
I have seen recommendations for the CM 7777 Preamp, which looks to have
around a 25dB gain (and apparently only available over the internet in
my area - Orange County, CA). There is a GE "22dB Video Signal
Amplifier" at Home Depot for half the price. Should I see much of a
difference between the two? I put the amp near the antenna, behind 3
feet of RG6 coming off the 4228 and it goes through 50 feet of RG6 to my
set.

In article Mark F writes:
I have a CM 4228 in my attic going through a cheap 10dB amp and usually
pick up most of the signals in my area, but occasionally have drop outs.
I have seen recommendations for the CM 7777 Preamp, which looks to have
around a 25dB gain (and apparently only available over the internet in
my area - Orange County, CA). There is a GE "22dB Video Signal
Amplifier" at Home Depot for half the price. Should I see much of a
difference between the two? I put the amp near the antenna, behind 3
feet of RG6 coming off the 4228 and it goes through 50 feet of RG6 to my
set.


A more important factor is the noise figure for the amp, not the overall
gain.

Second is the dynamic range, which affects resistance to overload and
intermodulation.

Third is the weatherproofing for putting the amp outside.

Fourth is the gain.


You could probably improve signals about 4 dB by putting the antenna outside,
but a good low noise preamp may help near that much. If you spring for a preamp
with a 2 dB noise figure, you will probably be about 4 dB better than the cheap
one you have, so it would be approximately equivalent to putting the antenna outside.
(Of course, outside will be higher, so there is more to benefit there.)

http://www.hdtvprimer.com/ANTENNAS/sizing.html
http://www.hdtvprimer.com/ANTENNAS/siting.html

Both of those sites will help you with some o the quirks of the things you
can look for.

Alan

"Mark F" wrote in message
...
I have a CM 4228 in my attic going through a cheap 10dB amp and usually
pick up most of the signals in my area, but occasionally have drop outs.
I have seen recommendations for the CM 7777 Preamp, which looks to have
around a 25dB gain (and apparently only available over the internet in
my area - Orange County, CA). There is a GE "22dB Video Signal
Amplifier" at Home Depot for half the price. Should I see much of a
difference between the two? I put the amp near the antenna, behind 3
feet of RG6 coming off the 4228 and it goes through 50 feet of RG6 to my
set.

The CM preamp is designed for the level of signal coming off of the antenna
and likely has a lower noise figure. The GE is likely a cheap distribution
amp and probably more noisy. Also, the CM is likely designed to be
weatherproof and designed to be mounted on the mast at the antenna, which is
where you want it.

Leonard

On Mon, 14 May 2007 20:08:44 -0700, Mark F
wrote:

I have a CM 4228 in my attic going through a cheap 10dB amp and usually
pick up most of the signals in my area, but occasionally have drop outs.
I have seen recommendations for the CM 7777 Preamp, which looks to have
around a 25dB gain (and apparently only available over the internet in
my area - Orange County, CA). There is a GE "22dB Video Signal
Amplifier" at Home Depot for half the price. Should I see much of a
difference between the two? I put the amp near the antenna, behind 3
feet of RG6 coming off the 4228 and it goes through 50 feet of RG6 to my
set.

I'm also in Orange County, CA and have the CM 7775 on order, along
with a DB8 antenna. It's my understanding that the 7775 is a Ch 14-69
UHF amp with a 2.0 dB noise figure and 26 dB gain. The 7777, as I
understand it, also amplifies in the Ch 7-13 area, high VHF. I did not
buy it because I'm keeping Cox Cable in O.C., at least what they call
"Basic" and "Expanded Basic" service, which should provide whatever is
offered on those channels after the 2/09 changeover + others like the
"History Channel," etc.. So, all I need is 14-69 for the HD channels.
Since you're also in O.C., you might do the same as I am. I believe
the 7775 is a bit cheaper than the 7777 too. In regard the DB8
antenna, I chose it in place of the highly recommended CM 4221 as I
(again) don't need the abily to receive 7-13 and the 4221 is a little
bigger than the DB8, and, being in an HOA area, I want as SMALL an
antenna as I can get to keep screaming and hollaring neighbors to a
minimum.

In regards mounting an antenna outside... At one point in my RF
career, prior to returning to college, I was a two-way radio
technician in this area and serviced mountain top radio repeaters on
Santiago Peak in O.C. and Mount Wilson in L.A. County. Naturally, part
of the work involved climbing MANY antenna towers over the years. I
learned that to keep an antenna and its feed cable working thruout the
year, sun, rain, snow, and ice, it's VERY important to INSULATE the
point at which the cable connector attaches to the antenna to seal it
from the elements. What was standard at the time, in the 2-Way radio
industry, was to first attach the connector and tighten it. Then we
would wrap the connector using black electrical tape; add enough tape
to extend about two inches either side of the screw-on connector, if
possible. THEN, liberally apply a thick coating of silicon grease, (we
called it "goose grease"), over all the electrical tape and perhaps an
inch beyond the tape on both sides. The silicon grease will "take a
set" and protect the connection from anything short of a lightening
strike. g

Jim
San Clemente, CA