JohnE
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Posts posted by JohnE
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Otto as mentioned makes pretty good stuff. Used them for many yrs in PS and commercial LM.
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at the very least there should be an isolator on both transmitters for IM , mixing and protecting the PA's from a bad antenna.
Did this in the 80's w/2 remote base's 700kC's apart. Much easier w/frqs that close. I think the total loss was 3dB overall.
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its called ducting and yes it can and does happen under the right conditions. mostly weather related.
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have a look at the PCTEL (old antenna specialist) ASP7795 Mosaic antenna 3dBd
https://d3dqzy9ky05fbv.cloudfront.net/wp-content/uploads/2020/06/ASP-Mosaic-Series.pdf
been using them for yrs, mostly 5dB version but the 3 is short enough to clear most garages on top of an SUV or mini van.
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I've seen and measured their duplexers. losses pretty much on the money .
typical real world loss I have measured was 40 in 28-32 out so that would be around 1dB loss or a little more.
just an FYIJE
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I always referenced between two mountain tops in a vacuum and then it was a maybe.
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WOW 400 bucks ouch.
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https://rfguys.com/products/kenwood-kmc-14-replacement-kmc-27c-6-pin-mic-tk-730-new
this is what you are looking for KMC 27C mic
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the 8400 is more than adequate for GMRS use. I can't begin to tell you how many I have out there in commercial service that see pretty much 100% tx time at least during daylight hrs.
have there been failures, yes there have but that is true of any radio that sees continuous use. I have had a string of MTR failures in the past 2 months. had 4 supplies, 3 PA's go south and 2 that just software fails w/no recovery.
nothing is fool proof.
JE
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On 8/27/2021 at 3:04 PM, Guest Bob said:
I just got a VXR 7000 and want to make sure I hook the external duplexer up correctly.
The VXR was programed for GMRS and I do have a license. Programing is 467.5500-467.7250.
Thank you
that programing will not work
462.xxxx/467.xxxx is how it should be programed.
concur w/Radioguy7268 also
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I will post this again as it is universal to all RF
dB loss power loss in %
0.5 10 100W in 90W out
1.0 20
1.5 30
2.0 37
2.5 44
3.0 50
3.5 56
4.0 60flat packs tune for Notch/Notch ----\___/----\___/----and should never be tuned W/power
typical loss for the ones I use are 1.5 or less most ~1.
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https://www.amazon.com/Nashua-Multi-Purpose-Length-Width-Aluminum/dp/B002EX855S
also available at home depot
use it all the time to make ground planes in fiberglass vehicles.
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the "pulse" can be turned off on some controllers.
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LTR falls w/in the rules as far as sub audible tone goes, its no different than tone/DCS as it is under 300 cycles.
now doing multiple machines linked together as a system is another story.
W/8 channels so close in frequency each machine would have to have its own filters and antennas if it were done at a single site.
you would have to have some really heavy use to warrant that kind of set up.
QuoteMy understanding of LTR is that there isn't a control channel, the control data is a burst included in the voice channel, and you stay on the frequency you are on, unless the data burst indicates a change
in LTR there is a home rptr # ,area bit, and the encode/decode data. all the steering is done by the controller.
did this yrs ago when I had some trolls playing w/my machine a little too much. I made it switchable form conventional to LTR over the air.
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I have found radio mobile to be pretty accurate once you dial it in correctly.
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I would run a propagation map to see what it will take to achieve that and if it can be before pushing any higher
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Yes, absolutely change the cable. 400 is not capable of handling a strike. If it were 1/2" or 7/8" hard line I would say give it a go.
ground the pipe and get yourself a poly phaser to at least give you some protection.
just my thoughts
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a little light reading
https://www.blm.gov/sites/blm.gov/files/Lands_ROW_Motorola_R56_2005_manual.pdf
note: this is from 05 , there have been updates
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you can turn them up but be aware that a lot of the used radios can be a little "soft" after yrs of service already.
the pins on the brick sometimes need to be "touched up" w/an iron as they get heat fatigued.
just an FYI
Base Antenna Issues
in Technical Discussion
Posted
I posted this a few yrs ago.
https://forums.mygmrs.com/topic/252-cable-types-and-losses