Hi Kent: Do not forget about coax loss. On 2-meters is not a huge issue, but in a car 440 coax losess can be 1.3-1.5 db for 13-15 feet of coax.

The comet CM-5m mag mout is using 13 feet of RG-58A/U coax. Loss at 435 will be near 1.3db, just of for the coax.

for satellelite work in the car, i use 2 mag mounts and a splitter. on 2 meter mono band 5/8 wave fill size vert. on 440 a mono band colinear stacked 1/2 verts.

45 degree passes on ISS 145.800 are no problem. FM birds are ok too, when the band is empty.

Here are some number I put together on coax loss for the typical mobile installation. dB Loss dB Loss Type Freq/Length Max Freq/Length Max Center 440 440 Pwr 900 900 Pwr Size Conductor

Feet 15 100 15 100

RG-58/U 1.5 9.9 105 2.2 14.5 60 .195" .032

RG-58/A 1.5 9.9 105 2.2 14.5 60 .195" Stranded

RG-8X 1.2 8.1 250 1.8 12.1 150 .240" Stranded

LMR-240UF 0.5 3.2 380 0.7 4.7 260 .240" .059

RG-58 comes in many flavors, No letter, A, C and U U sometimes is a solid 20 AWG copper center. A and C have a stranded center conductor. The center conductor size would be similar to solid, but will have a little more loss.

Most cars will need 15 to 17 feet of coax. RG-8X and LMR-240 have the same Outside diameter (.240"), however the LMR has a foil shield and half the loss of RG-8X. The LMR-UF-240 version is the Ultra Flex flavor and can bend easier.

From this list of small car style coax, the LMR beats

them all, in lowest loss for the size and highest transmitter power loads. I was planning on installing a 440 AMP in my car, but after looking at the coax, I realized that I would fry the RG-58 coax at 100+ watts on 440mc.

I dissected an old Larsen Magmount and replaced the original RG-58U with LMR-240-UF. I have been running this configuration for over a year with good results and I have not melted any coax. There is also a nice added benefit, in the winter time during a long rag chew on 440, the 440 amp keeps the passenger seat warm.

For those of you interested in 900 mc, the benefits are even greater.

900 mc 10 watts, in, 15 feet of LMR-240, = 7.7 watts out 10 watts, in, 15 feet of RG-58/U, = 5.8 watts out

Power reference http://www.ocarc.ca/coax.htm

73 Miles WF1F

--- "Kent R. Frazier" [email protected] wrote:

I have been unsuccessfully trying to hear AO51 over the last week with my mobile rig (Icom IC2720 with a Comet C767 dual band antenna mounted to the rear hatchback with a Comet CP-5M mount).

Since I am able to transmit and receive on our local repeaters, I'm guessing that the issue is with my antenna. I've been using the online AMSAT satellite pass predictions to predict passes I try to listen to.

Can anyone recommend an antenna I could use with the above mount to improve my satellite reception? I'll settle for reception at the moment. I have a 2m handheld (Icom T-22A) that I've been thinking of using for transmit. I'm thinking of adding a Arrow antenna for this.

I'm not that knowledgeable with regard to antennas currently, so specific models would be helpful.

Thanks,

Kent

-- Kent R. Frazier, K5KNT _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

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