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Author Topic: 23 cm (1240Mhz) in Los Angeles, getting started?  (Read 1203 times)
N6YFM
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Posts: 498




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« on: August 01, 2017, 09:53:17 PM »

Hi Team:

I just acquired my first radio that is capable of 1240-1300Mhz, an old Kenwood TM-642A with a 1200 module.   I have a couple questions before I invest too much in this;

What are some 23cm open repeaters that are actually active in Los Angeles, and likely reachable
from the coastal areas (just south of L.A.X airport, or Torrance area?

What is the typical coverage range for a 23cm repeater?  If it was on Mount Wilson, could I work it
from Torrance or Redondo Beach with a base antenna?

Does anyone have suggestions for a 23cm antenna?  This would be for base use to try out the band.
I would rather not put up a $185 base antenna until I first see how much activity there is in the area.
Can a lower cost or simple antenna give an idea of what the usage is locally?

Thanks for your guidance.

Neal
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W8JX
Member

Posts: 12080




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« Reply #1 on: August 02, 2017, 07:49:23 AM »

On 23cm the height and gain of antenna is VERY important as that band is more line of site than 440 and even foliage can effect it. Also length and type of coax becomes a factor on 1296 as even LMR 400 looses nearly 5db on a 100 foot run. On any run much over 75 feet you should consider using 1/2 inch or bigger helix cable. Man made noise is not a issue on 1296 but internal noise figure in rigs start to rise above 440 levels which limits usable sensitivity so you really want to minimize line loss on this band. 1296 has potential but it was never exploited much because lack of commercial gear for it. That could change just like 5ghz wifi was under used for many years but is not seeing a lot of use with newer technology.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
ONAIR
Member

Posts: 3525




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« Reply #2 on: August 03, 2017, 08:03:10 PM »

Hi Team:

I just acquired my first radio that is capable of 1240-1300Mhz, an old Kenwood TM-642A with a 1200 module.   I have a couple questions before I invest too much in this;

What are some 23cm open repeaters that are actually active in Los Angeles, and likely reachable
from the coastal areas (just south of L.A.X airport, or Torrance area?

What is the typical coverage range for a 23cm repeater?  If it was on Mount Wilson, could I work it
from Torrance or Redondo Beach with a base antenna?

Does anyone have suggestions for a 23cm antenna?  This would be for base use to try out the band.
I would rather not put up a $185 base antenna until I first see how much activity there is in the area.
Can a lower cost or simple antenna give an idea of what the usage is locally?

Thanks for your guidance.

Neal
  I would try a homebrew antenna first before spending a lot of money.  A small beam may actually be your best bet.
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W8JX
Member

Posts: 12080




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« Reply #3 on: August 04, 2017, 05:34:05 AM »

  I would try a homebrew antenna first before spending a lot of money.  A small beam may actually be your best bet.

Antenna gain and height is very important on this band. a small beam would likely not be choice because it would only have gain in one direction. There are some very high gain vertical antennas for that band. There should be a lot of 1296/23cm activity in your area as there is a lot of repeaters listed. If you start with a marginal antenna at a low height too you could get a bad feel for the bands potential. You do not want to cut too many corners on antenna or height on this band. And by height I am saying maybe at least 30 feet for starters.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
W9FIB
Member

Posts: 2094




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« Reply #4 on: August 11, 2017, 09:14:25 PM »

A beam is a great choice since you can point it at the repeater site and gain distance you can work the repeater. That's the idea of a beam is to concentrate the signal where it is intended to go, not just heating up the entire atmosphere around you. And when you change repeaters, swing the beam in that direction. People been doing that in rural areas on 2M and 440 for many years. For some, that is the only way they can use repeaters.

And on 23cm the beams are so small, easily built, and can be turned with cheap little TV antenna rotors. A plus for the budget minded operator.
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