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Author Topic: Why are radios lower power on AM and UHF  (Read 2211 times)
MDNITERDER
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« on: September 13, 2012, 02:47:03 AM »

 This is something I have always wondered, Why do all manufactures make there radios have lower power on AM and UHF?
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KB4QAA
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« Reply #1 on: September 13, 2012, 06:59:40 AM »

With AM you have to consider where all the input power is going.  Assuming our hypothetical radio specifications are for 100W SSB.  All the power is going into that one sideband.

For AM, same input power has to be split among the Carrier, Upper and Lower sidebands.  So that is why you may see the AM output listed as anywhere from 25-40% of the SSB output spec.

Regarding UHF, I've always assumed that the lower output was based on the higher cost of components and design limitations with the manufacturer choosing to provide a lower cost radio.   In any case, compare the power outputs in dB, not Watts, and the difference is probably minimal.
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KJ6MSG
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« Reply #2 on: September 13, 2012, 08:04:03 AM »

Also more "taxing" and difficult in terms of design and components to generate 50W at 2m frequencies and 50W at 70cm frequencies.
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73,
KJ6MSG
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W5FYI
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« Reply #3 on: September 13, 2012, 09:15:35 AM »

And you don't necessarily need much power on UHF when your communication range is generally limited to line-of-sight.
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W8JX
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« Reply #4 on: September 13, 2012, 09:41:55 AM »

This is something I have always wondered, Why do all manufactures make there radios have lower power on AM and UHF?

It has a lot to do with the mode. Unlike SSB or CW that has period of time with zero output, AM has a constant carrier. Also AM PEP out power is about 4x the carrier so 25 watts carrier is 100watts PEP. On FM power output is constant placing a higher load on final and also as frequency goes up through VHF and UHF ranges the efficiency drops further increasing heat load on finals.
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MDNITERDER
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Posts: 146




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« Reply #5 on: September 13, 2012, 01:09:04 PM »

 All good answers thank you very much.

 My reasons for asking these is GMRS seems to be my only option at this time, I have done a lot of studying, even doing pretests, studding the Q/A pool and when I do a pretest still get mid 60% and with a GMRS license is 80$ per person

 I have a family member that is 35 miles away and we would love to use the radio for back and forth communications and also when we are off roading. on our ATV's

 I would love to obtain my ham license but it appears it was not meant for me.
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W5FYI
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« Reply #6 on: September 13, 2012, 01:28:01 PM »

Citizens Band, anyone?
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AE4RV
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« Reply #7 on: September 13, 2012, 01:46:43 PM »

Keep studying, you can do it.
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MDNITERDER
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Posts: 146




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« Reply #8 on: September 13, 2012, 02:04:00 PM »

Citizens Band, anyone?

 Oh god no, please no, I do not need the ignorant conversations that appear on there. The Some or most of the CB users  are extremely barbaric/prehistoric, Me radio stronger than yours, Squash. Me channel master you do as i say, 15 channels of bleed over. No thank you sir. I pass.

 I also hope that was not an attack on my intelligence.  Undecided
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WB2WIK
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« Reply #9 on: September 13, 2012, 03:57:31 PM »

All good answers thank you very much.

 My reasons for asking these is GMRS seems to be my only option at this time, I have done a lot of studying, even doing pretests, studding the Q/A pool and when I do a pretest still get mid 60% and with a GMRS license is 80$ per person

 I have a family member that is 35 miles away and we would love to use the radio for back and forth communications and also when we are off roading. on our ATV's

 I would love to obtain my ham license but it appears it was not meant for me.

GMRS might be a better option, since to use ham gear you'd both need ham licenses -- you and your family member; so even if you pass the test just fine, they would need to, also.
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MDNITERDER
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« Reply #10 on: September 13, 2012, 04:00:43 PM »

GMRS for us both is fine, but I always wanted to explore what radio had to offer, Meeting new people, learning new things about radio's Maybe meet someone interesting,
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KE5JPP
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« Reply #11 on: September 14, 2012, 04:54:29 AM »

All good answers thank you very much.

 My reasons for asking these is GMRS seems to be my only option at this time, I have done a lot of studying, even doing pretests, studding the Q/A pool and when I do a pretest still get mid 60% and with a GMRS license is 80$ per person

 I have a family member that is 35 miles away and we would love to use the radio for back and forth communications and also when we are off roading. on our ATV's

 I would love to obtain my ham license but it appears it was not meant for me.

Another option is MURS http://en.wikipedia.org/wiki/Multi-Use_Radio_Service which is just above the 2 meter Ham band.  With a decent directional antenna, 35  miles is no problem.  All members of the family can use it license free.

Gene
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