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Author Topic: small hf amplifier in my car?  (Read 928 times)
CHRISDX
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Posts: 244




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« on: March 19, 2010, 06:30:28 PM »

possible dumb question... i have an icom 706mk2g in my car with a tarheel.  i'm just getting it set up.  someone in another thread mentioned using an amplifier to compensate for the the relatively poor antenna efficiency of any whip on a car.

the tarheel I have can support up ro 200 watts. so, is there an amp that can run hands free on the hf bands and would provide that output power level?

thanks
chris
kb1snj
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WX7G
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Posts: 6041




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« Reply #1 on: March 19, 2010, 06:51:09 PM »

You are already at 100 watts. Going to 200 watts is not that much of an improvement. But an Ameritron ALS-500 (500 watt amp for $750) can be run at 200 watts.

If you're going to spend that much money you might as well sell the Little Tarheel II and buy a Little Tarheel II high power to go with the amp.

This weekend I install the ALS-500 in my Smart Car. I'm having great success on 20 meters at 100 W working DX on CW driving to and from work. The antenna is an MFJ base loaded 4' whip mounted at the roof line.

An antenna upgrade to a 7' Hamstick and the 400 W (CW) amp should give me about 10 dB more signal.
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K0BG
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« Reply #2 on: March 20, 2010, 04:29:35 PM »

Chris, if you visit my web site, and do a little reading, you'll find out just how to get the most out of your mobile.

If you're using the Lil Tarheel, you're kidding yourself if you think an amp will help. The real key is getting the most of of the antenna first, and then thinking about an amplifier. Fact is, most mobile installations which include an amp, would have been getter off doing a decent antenna installation. Even as a newcomer, you can't imagine how bad some of them are.

The ALS-500 sells now for just over $850, and by the time you install one correctly, you'll be spending upwards of $1,200 to do it right.
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CHRISDX
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Posts: 244




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« Reply #3 on: March 27, 2010, 04:12:12 PM »

That k0bg site is terrific for info, and well organized.

I did take off the tarheel and installed a 102" stainless "cb whip", and installed my AT-7000 tuner.  This new combo loses me the ability to tune 80m, but I can tune down to 40m with it.

Today I made very high quality contacts on 17m in Africa and Mexico.

I only wish the tuner would get this antenna to 80m.  Also, I would like to shorten the whip by a couple feet but I dont want to lose 40m too.

Anyway, now suppose that I could install a 500w amp and compensate for the likely single digit efficiency of a mobile whip. I have been reading the reviews here on various amps, the Ameritron ALS-600 looks interesting.

Also, if there is an auto tuner that could get the whip down to 80m (and work half decent) please let me know.

Thanks
Chris
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WX7G
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« Reply #4 on: March 29, 2010, 07:27:18 AM »

A dB is a dB whether it comes from an antenna improvement or an increase in power. What we are after hear in mobile operation is more transmitted signal and not more received signal.

The ALS-500 runs $750. By the time I installed it I have $780 invested. Given the electrical system in my car it runs 300 watts of CW. That is a 5 dB increase over the 100 W transceiver.

I suspect the Little Tarheel will run fine at 300 watts PEP. I have run mobile antennas at twice their rating on CW but due to the low duty cycle they survive.

As analyzed in another post, given your antenna height restictions, an all-out short antenna will give you 3 dB or so over the Tarheel.  

If the biggest signal is what you want max out the antenna AND install an amp.
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