Power cable question

[ohiomgman]

I am instaslling a 2060 power source on my M151A1. I will be using the MT1029 mount to secure a PRC77 radio. I will also be installing a MT 1829 mount for the R442 radio I will be installing later. How does/which cable, directs power from the 2060 power source/MT1029 mount...over to the MT1898 mount/R442 radio?

[Rainman]

Hey OMGM,
The cable you need is the same one Ralph is working on acquiring on this thread. http://g838.org/viewtopic.php?f=5&t=3798 The one I have to mount my 1829 is a little longer than necessary, but it loops up under the 1029 and the excess isn't visible, so the length for me is not critical unless it's too short. It runs from mount to mount.
Rainman

[tbanks]

The cable your looking for is the CX4721.I have them in 2'6" and 4' lengths.

[ohiomgman]

The cable your looking for is the CX4721.I have them in 2'6" and 4' lengths.

I am compiling a list of cables I need to complete my instalations. When I am satisfied my list is complete I will order up.

I am still on the bottom edge of the radio learning curve.

[ohiomgman]

Hey OMGM,
The cable you need is the same one Ralph is working on acquiring on this thread. http://g838.org/viewtopic.php?f=5&t=3798 The one I have to mount my 1829 is a little longer than necessary, but it loops up under the 1029 and the excess isn't visible, so the length for me is not critical unless it's too short. It runs from mount to mount.
Rainman

A bit to long on a power cable seems like no big thing. My understanding is that it is BAD to coil up the coax running from your radio to your antenna...if it is to long. Is that true?

[raymond]

Any time you coil up any cable with power running through it, it will generate a magnetic field. I could see how this would cause radio interference and frequency drift. If the power going through the cable is substantial, it will generate heat. Try plugging in a vacuum cleaner to a tightly coiled extension cord and run it for a while. Then feel the temperature of the cord. If you put another coiled wire next to the one you are running power through, you can induce a current into the second cord. A transformer is essentially 2 electric lines coiled up and intermingled.

[Rainman]

Hey OMGM,
Yes and no. It's true that it can have a negative effect, but at the low wattage, short length of cable, and frequency of a PRC-77 it won't have any significant effect at all. If it did it would only be during high power extended transmissions. You planning any of those? Cable coils can have negative effects at much higher wattage, and more so in the UHF and VHF bands, but nothing to worry about in less than 25' lengths on HF. Remember, unlike an extension cord, this cable has a braided shield to protect the signal inside. When operating a high power stations for maximum efficiency, transmitting coaxial cables can be cut to match the wave length, and may have in line tuners to reduce reflected power and signal loss. Your MX-6707 has a built in tuner that can be operated automatically or manually. That's the dial on the bottom of the antenna base. I need reading glasses to see the position these days, but no worries for a few coils of spare antenna coaxial cable.
Rainman

[Ralph Fuller]

The information you need has just been put into the Wiki. Just click here:
http://g838.org/wiki/doku.php?id=vrc_radio_installation

[raymond]

Not sure at what wattage a coil in the coax affects transmission, but on my boat, I have a 25 watt marine band radio. My Shakespeare antenna manual says not to shorten the coax cable when installing. It said it was cut to a length that facilitates transmission and reception. If the cable is too long, they recommend coiling it up someplace where it will be out of sight.

[Rainman]

Hey Raymond,
Yep, they tune the antenna to the middle of the marine band and cut the coax to the closest 1/4 wave length to minimize the Standing Wave Ratio, a measurement of how much transmit power is not leaving the antenna when you key the mic. Your dealing with UHF and 5 times the transmit wattage of an HF freq PRC-77. Our MX-6707's auto adjust the relative length of the antenna for the minimum SWR. On the receive side, exact antenna tuning is less important. The receive antenna for the R442 is actually made up of 4 elements. 2 ea MS-116, 1 ea MS-117, and 1 ea MS-118. 3 sections are more commonly used in the hobby to more closely match the visual length of the AS-1729 2 section RT-524 antenna, but 4 is what I learned in at Ft Gordon signal school.
Rainman

[Ralph Fuller]

Ohiomgman: When you are installing the CX4721, 4 pin cable, there is a slot on the cable, and a tit on the radio-mount that must line up. Then raise and turn the handle clockwise on the cable to secure it into the mount.
A 3'0" cable fits underneath without any coiling.

[rickf]

Hey OMGM,
Yes and no. It's true that it can have a negative effect, but at the low wattage, short length of cable, and frequency of a PRC-77 it won't have any significant effect at all. If it did it would only be during high power extended transmissions. You planning any of those? Cable coils can have negative effects at much higher wattage, and more so in the UHF and VHF bands, but nothing to worry about in less than 25' lengths on HF. Remember, unlike an extension cord, this cable has a braided shield to protect the signal inside. When operating a high power stations for maximum efficiency, transmitting coaxial cables can be cut to match the wave length, and may have in line tuners to reduce reflected power and signal loss. Your MX-6707 has a built in tuner that can be operated automatically or manually. That's the dial on the bottom of the antenna base. I need reading glasses to see the position these days, but no worries for a few coils of spare antenna coaxial cable.
Rainman

Do you mean I might have problems if I hook up my 150 watt bi-lateral linear amp?