[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: NEED YOUR OPINION



James,

I just got home from a three-day business trip, so don't know if others
have given you an answer.  

I am using an FT-847 and the M2-436CP42U/G (I added a 60w amp near the
antenna to eliminate line loss...just using RG-213 which looses half my
power to the antenna).  The advertised gain for the antenna is 16.5 dBd
(18.6 dBi).  The standard installation is for RHCP so the gain is correctly
expressed as 18.6 dBic.  So if you have 50w Tx output this will result in
an EiRP = 50 * 10^(18.6/10) = 50 * 72.4 = 3622w.

That's a whole lot of uplink power!  In practise I have operated into AO-40
using as little as 5w (EiRP = 362w).  So YES, this antenna will easily work
AO-40!  In fact you probably can get away using a 13 dBic antenna with 25w
(EiRP ~ 500w) for squint angles under 10 degrees.  That might become
somewhat marginal as the squint angle gets larger so having a little more
gain/power is nice.  The drawbacks for the 436CP42 are its cost and its
length.  The advantage is it works darn well and can be used for the
FO-birds and AO-10, easily.  Mine is mounted on a Yaesu B5400 az-el rotator
with no ill-effects!  Using a 5-foot aluminum cross-boom with the 33-inch
dish on the other end.  The M2 antenna is mounted in the "x" configuration
and the LMR-400 cable dressed down the antenna and across the boom with no
discernable bad effects!

I do not remember what Cushcraft claimed for the gain of the 416TB (I had
two for AO-10), but I think 13 dBic is close.  You have to consider that
your feedline type and length can effect the amount of power reaching the
antenna. For best results use either Belden-9913 or Times LMR-400 (my
preference).  Either of these can be bought from ham suppliers for around
$0.59/foot; proper 9913/LMR-400 N-type connectors run about $6 (I like the
RFN 1002-1Si from www.rfparts.com) .  50-foot of either will result in only
0.8 dB transmission loss (83% of the power will reach the antenna).  Or you
can do like I did and install power amp near the antenna (in fact a 100w PA
in the shack will have ample reserve power to overcome loss in 50-foot of
RG-8/RG-213 type cable if mounting equipment at the antenna is
inconvenient).  

James, I see you are using 9913.  How old is it?  Measure the loss and SWR.
 Be aware that 9913 is highly susceptible to invasion by moisture which
will "kill it" for low-loss operation. If in doubt replace it...you might
be pleasantly surprized how much difference it will make!  Be sure that
cables/connectors are well sealed from intrusion by rain/snow (in Calif.?). 

If the 416B is kind of old, quite a bit of aluminum oxide corrosion may
have built up between the elements and the boom and the phasing cables may
have gone bad.  Hopefully you have measured the SWR at the "tee" connector
and loss of the phasing lines.  If the antenna is refurbished (taken apart
and scrubbed) and working well then I would think it adequate for use with
the FT-847.

To reduce this to a simple choices:
1)  Get either the M2 436CP42 or the 436CP30.
2)  Get a PA and check over the 416TB antenna.

I made these comments more general than your question so others with
similar question could benefit!  

GL, Look for you on AO-40!

Ed, AL7EB
PS:  my mode-US antennas are now temporarly restored to operation; mode-L
will likely move to my 8-foot dish late this summer!  The 45-elem 1296
loop-yagi is now 20-elem long after hitting the roof and breaking in half
when the wind tipped over the whole array :-)

At 06:58 PM 6/27/2002 -0500, James Kennedy wrote:
>Here is my problem, I have the Crushcraft ( OLD) AOP-1 system and the 435
>antenna does ok on the Leo birds. I have yet to get a contact on AO-40! I
>think it's my uplink antenna the crushcraft 416TB. I was looking the buying
>a 70CM amp or replacing the antenna with M2 436cp42 u/g; does anyone on the
>list have this M2 antenna?
>
>1. If so how do you like it?
>
>2. what are the draw backs to it?
>
>Here is what I'm using Radio Ft-847
>                       coax  9913fx
>                       antenna crushcraft 416TB
>                       down converter  (k5gna) system
>
>any help ?
>
>
>73's de Jim
>WH6LR
>
>----
>Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
>To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> 

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home