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  #11  
Old 01-19-2012, 10:28 AM
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Default let the "shell" game begin...

Quote:
Originally Posted by pskhaat View Post
Well, let me know on the 8800. I had my 8900 head unit stolen out of my vehicle some time back. I'm debating either replacement or picking up a used radio (nearly the same $) but don't honestly need 6m & 10m FM ...
So.....if you decide to sell the 'brains' of your 8900 I might be interested. I have an 8900 in my 60, might be cool to have the same at in the shack or in my 40. I'm sure I could move faceplates back and forth.

OH wait...just re-read...sounds like the whole thing got nabbed, not just the faceplate.

Last edited by CardinalFJ60; 01-19-2012 at 10:29 AM. Reason: re-read.
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  #12  
Old 01-19-2012, 10:45 AM
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I had an 8800 in my 40 and decided to sell it and use a 2900 instead. I never used the 70cm and although I miss being able to listen to both the simplex and repeater at the same time, I don't miss how tiny and delicate the 8800 seemed to be compared to the 2900. The 2900 is much better suited to being in an open 40. I put a 2800 in my Hilux as well. They are both easy to use, easy to see, and have tough construction. I also like the higher power of the 2900 and 2800 for peace of mind when I'm far away from repeaters and cell coverage.
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  #13  
Old 01-19-2012, 10:00 PM
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As I've said like 8800x now, I have the 8800 and love it. But I'm curious where you'd mount a 2900 in the 100- the remote face seems to be the default for the 100 series setups, mainly due to lack of space, or not wanting to bolt on a knee buster.

and to answer the original question, I've only used 70cm once just to say I did.. but I'm on two 2m channels all the time.
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Old 01-20-2012, 11:15 AM
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Thanks Nakman-
Center console big enough for the 2900? I assume most controls can be operated via mic buttons. I would do an external speaker on the passenger side. Heat issues? I don't want a knee buster for me or passenger. For a remote setup, I really like the use of the sunglass holder but won't let me. Somewhere on the dash would have to work.

And one more probably dumb question. Is it possible at all to use 70cm with a 2m antenna? even at a reduced capacity?
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  #15  
Old 01-20-2012, 11:54 AM
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I can see this weekend if a 2800 will fit, I have one that's not installed in anything right now. I believe it's the same size radio. Yeah heat is a concern, but others seem to be doing it with no ill effects, so your call on if it's an issue. Depends on how much you transmit, and at what power, and how well tuned your antenna is... kinda hard to get a straight answer. IMO the remote faceplate under the heater is best, with the head unit either under the passenger seat or behind the back cargo panel.

And yes, you could technically blast any frequency through any antenna with some reduced capacity, sure -think of all the home brew antennas out there. But the performance loss on transmitting gets converted to heat, which in a worst case would potentially let the smoke out of the radio? I'm sure a few transmits you'd be fine, but prolonged use probably not a good idea. It's easy enough to get a dual band antenna in the first place though, I think the SBB-1 goes both ways and it's a cool little stubby for trails.
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  #16  
Old 01-20-2012, 12:47 PM
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Quote:
Originally Posted by nakman View Post
And yes, you could technically blast any frequency through any antenna with some reduced capacity
NO!

The relationship of 145MHz to 445MHz is such that they do not share a 1/4λ multiple fundamental. If you key on 70cm into a 2m antenna it's probably going to see a high reflection.

There are ways to make this work, a gamma match or making the antenna into a sleeved dipole, etc. But typically mobile monopole whips use a trap to make a long antenna electrically correct for 70cm, say a 1/4λ 2m into a 3/4λ 70cm or 1/2λ 2m into a co-linear 70cm.

All solid state radios made now necessarily (tube radios tolerate high SWR much, much better) shut down on high SWR, which is why you could probably key up and not ruin your radio. It might even leak a little RF onto the antenna, but it won't be much (like milliwatts).

If you do it long enough with high enough power, you'll fry the protection shunt. It's all about heat, any power not doing work exciting electrons (which requires antenna resonance or apparent resonance with caps and inductors helping) is converted to heat, which is the sworn enemy of transistors.
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  #17  
Old 01-20-2012, 12:57 PM
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Wow, thanks for the lesson in radio frequency theory.

I like that little SBB-1. I look forward to hearing about the fitment of the radio.

Just found this great thread on Mud that I think I might try to copy after hearing your advice.

http://forum.ih8mud.com/80-series-te...1-install.html
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  #18  
Old 01-20-2012, 12:59 PM
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Dave I'm not sure we're saying different things.. as you still say it's technically possible, but not a good idea. agreed.

But if you were transmit on 70cm with a 2m antenna to a truck that's is 50' behind you, I'm not sure he wouldn't hear you. We can try with one of your radios..
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Old 01-20-2012, 01:06 PM
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Quote:
Originally Posted by nakman View Post
Dave I'm not sure we're saying different things.. as you still say it's technically possible, but not a good idea. agreed.

But if you were transmit on 70cm with a 2m antenna to a truck that's is 50' behind you, I'm not sure he wouldn't hear you. We can try with one of your radios..
You are very right that for RX the 2m antenna would be marginally different in the real world than a tuned antenna on 70cm. It's possible that a 5/8λ 2m might even receive slightly better than a proper 70cm.

I read that this was for TX on 70cm potentially using a FT-8800 with a 2m-only antenna since the FT-2900 does not even receive 70cm. That would not be a good idea at all.

The RF that comes out would be due to the incidental and reflected waves on the coax itself. The antenna wouldn't be doing much work. In reality it would almost the same radiated energy you get from a dummy load, which works BTW. Running 100W into a power resistor or even an incandescent light bulb radiates energy and you can actually hold a QSO using a light bulb as an antenna if band conditions are good. It takes quite a bit of power to do that and the field you generate is about equivalent to a super QRP radio into an tuned antenna (think 200mW).
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  #20  
Old 01-20-2012, 04:19 PM
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Default variation on this 70cm thread...canyons??

so...when Martin, Perry and Sean were guiding me down to Blue Notch the 2m signal would come and go based on the part of the canyon I was in, how deep/tall is was, etc. Makes sense.

The discussion then started about whether or not 70cm would have been more effective since it would tend to 'bounce' a little better. I think it would have been a little better but we never tried it.

What say ye??
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