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HT750/1250 RF Terminator?

Posted: Fri Aug 29, 2008 9:37 am
by Two Tone
I'm looking to do some testing with my HT750 and HT1250 (46mhz range). Im looking to see if there is an RF terminator that I can buy and/or build for the HT series. Im sorta stuck and looking for some direction. Thanks!

Re: HT750/1250 RF Terminator?

Posted: Fri Aug 29, 2008 11:34 pm
by AEC
First thing you will require, is the adaptor that fits the radio.
Second, it's the same adaptor that is used on the GP300/P110 radios of old.

It is a threaded phono jack which transitions to a BNC-F connector.

Don't bother with Circle-M, they want far more than it is worth.

You should be able to hamfest this item for less than a $10.00 bill in the package.

As for the termination, get a quality 50 ohm load, NOT one of those cheaply assembled resistors in an aluminum tube that junk shack sells, or used to sell(they are a simple carbon resistor, and the 'heatsink' is only for show as it does not make physical contact with the termination).

Decibel makes a fine 30 watt load, or you can try Tessco, or Tulley's...actually, any good shop should carry quality terminations.
You can also find them on surplus Isolators/circulators as well.

I have several ranging from a simple 5 watt load, to a 'monster' 1,000 watt 'block' for high power testing.
Most are type 'N' female, with several others being of the type 'N' male.

A short run of cable(high quality), and a stable load is all you need.

Transisitions are easy to acquire from parts houses like Fry's electronics, ham radio stores like HRO, AES and R&L and so on...

Do NOT buy screw-on connectors as they are garbage and do NOT provide a measurable or repeatable 50 Ohm rating when swept with a bridge and monitor.

You can also contemplate the purchase of a power attenuator if you plan on keeping a transmit condition of a continuous nature.
This way, you can 'create' your own output levels using a combination of attenuators instead of a load.

Of course, these would appear like a load, but with a male and female connector on each end.

Re: HT750/1250 RF Terminator?

Posted: Sun Nov 23, 2008 1:15 am
by Two Tone
Can someone show me the proper connector to use?

Thanks!

Re: HT750/1250 RF Terminator?

Posted: Sun Nov 23, 2008 5:05 am
by W8RW
Hi Two Tone,

I think you can see what the adapter looks like in the epay ad:

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0155118210

W8RW

Re: HT750/1250 RF Terminator?

Posted: Sun Nov 23, 2008 5:29 am
by Tom in D.C.
The point to be made is that the GP300's antenna connector provides you with the
positive/hot connection only but no ground. If you use the suggested adapter then
your dummy load will have a ground reference, which means it will have a complete
circuit and thus will give you accurate and steady readings.

Re: HT750/1250 RF Terminator?

Posted: Sun Nov 23, 2008 3:14 pm
by Will
At 46 mHz you could build a "dummy" load resistor from four 200 ohm 2 watt carbon resistors in parallel.
Keep the resistor leads as short as possible. I built one on a BNC chassis connector.