JohnE
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Posts posted by JohnE
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have been using these for decades but single band
https://d3dqzy9ky05fbv.cloudfront.net/wp-content/uploads/2020/06/ASP-Mosaic-Series.pdf
also have been using a Laird B4505 for a few yrs now and I find it comparable to the Mosaic
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https://www.rfparts.com/relays/relays-tohtsu.html
http://www.advancedreceiver.com/page22.html
I' sure there is a way to make one of these for for you
found one more
https://www.w6pql.com/using_inexpensive_relays.htmand an article
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Effort is a gross understatement
back story..... not enough room for a fall zone , too much BS to put up a 125' tower. Have ~100' pine trees in strong health condition. Hire tree guy and he thinks I'm nuts but he's getting paid. Put the whole antenna ,pipe and cable attached together on the ground. strain relieved and stressed the cable before having it hoisted and mounted as one piece.
My only mistake in the was cheeping out on the antenna. So far it has served me well. -
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a little lite reading on grounding
https://www.blm.gov/sites/blm.gov/files/Lands_ROW_Motorola_R56_2005_manual.pdf
as to mast- while I agree EMT is a poor choice I have used 1" aluminum for many yrs on lightweight antennas (sub 6 lbs and <8') pretty much anything that has a bending moment of less than 75 ft/lbs. Most of the antennas that are made for our purposes fit that description.
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From personal experience wish I still had the pics
LMR 600 long story short the outer casing on the cable becomes porous and water migrates into it. at best in the NE 5-7 yrs and it needs to be changed.
As a sub for 400 I sometimes use FSJ 2. Similar size and loss
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Lolwhut? No, I'm not. S-meter calibration is different for HF and VHF. On HF frequencies S1 is 0.2uV, S2 is 0.4uV, S3 is 0.79uV and so on. On VHF it is 0.02uV, 0.04uV, 0.08uV... Why the 10x difference? Because it's not about microvolts at all.
Strength scale (the "S" in the RST):
- Faint—signals barely perceptible
- Very weak signals
- Weak signals
- Fair signals
- Fairly good signals
- Good signals
- Moderately strong signals
- Strong signals
- Extremely strong signals
Where are the microvolts? It is all about acoustics.
12 and 20dB sinad is all I care about. Where does it open and where does it close in CSQ or pl
- Radioguy7268 and axorlov
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Kenwood
TK 805d , 880, 863, 8160, 8180 and NX 5800
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hook up the yellow wire to 12V , it's an ignition wire. that is where you need to start before going down the rabbit hole
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29 minutes ago, tweiss3 said:
I think you have two options for RF linking. Though you do mention that LOS is troublesome for some RX sites, but you can do GMRS linking via simplex, but then you fall under the definition of fixed station and are limited to 15 watts. The second option would be IP linking over RF (using commercial dishes with type acceptance) but that is 100% LOS driven.
like a microwave backbone
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GPS would be for simulcasting to sync the transmitters timing. Also said transmitters would have to have a high stability XO to lock it on frequency.
You are need a comparator or something that works like one. seeing as you are using IP everything should come back to one "computer" and select the site w/best RSSI and as it moves it goes to the next. IIRC there was a HAM that had some you tubes on it. I think it was in relation to a simulcast set up.
hope this was some help -
Grounding is a double edge sword. most power supplies have a grounded plug(3 prong) that means it is grounded to your AC electrical system. The radio attached to it is in turn grounded as is the antenna connector on the back a chassis ground. You see where this is going.
At a minimum I would get a Polyphaser and make sure it has a proper ground that will offer some protection.The pic below is an example of a direct hit. Antenna was completely vaporized, connector too. The Polyphaser had to be removed from the ground bar w/hammer. the equipment (a city agency) was undamaged. The cable will most likely have to be changed as a precaution.
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Duplexer needs tuned. No way around it. Its not on the frequency you are trying to use.
Agreed. From what I have seen they are tuned 462/467 flat there in lies your problem. It's a half Meg out at a minimum and that's not gonna cut it.
I have seen some screen shots of properly tuned ones and they seem to be ok but have some power handling issues just an FYI
JE
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same thing in the commercial world. Difference being that anything out of the box "should" be checked before it goes out the door. I can site many examples of things like this. Big M SLR programed power 55W- reality 49.5-50 on a calibrated Bird watt meter into a calibrated service monitor. Kenwood mobiles out of the box are for the most part pretty on but do require minor tuning depending on Freq, generally the higher you go the lower the power. AT 450 you might get 48-49 but T-band 42-45 just as an example.
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Agree here w/Gortex.
SWR at the radio before the duplexer should be the same or slightly higher than the SWR looking at the antenna after the duplexer. Your losses "should" be ~25% depending on quality of the filter. (ie) 25w in ~19W out roughly.
stay away from that CCC.
JE
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And I imagine a duplexer would take away some of the power from the TX radio. It's putting out 24 w right now so a duplexer would probably take half of that.
stay away from those CC duplexers , they are made for a 10mC split not 5. find a celwave or a micro magic
here is a pc of 2 bp/br and a br/br duplexers as well as an Isolator and a receive preampas to losses the br/br small duplexer has an insertion loss of ~1.5 dB max typical when tuned correctly is ~1.1 that would be 20%. In your case that wold be ~5W loss
Jeep crawler you should have seen some of the sketchy stuff I had to make work for one reason or another.
JE
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It also depends on the duplexer itself. They however have to be tuned to a specific frequency.
a br/br(notch/notch) will be more "forgiving" than a bp/br(pass/notch) and even that varies manufacture to manufacture. most can ~500kC's, the GMRS "band" is only 175kC's
W/that being said a good br/br filter tuned to 462/467. 6375 "should" be able to handle all the GMRS channels w/o any real issues.
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1. Is this Tram Browning external antenna a good antenna for GMRS?
it will do the job. comparable to Maxrad /Pctel type antennas.
Quote2. Can I re-use this DTV coax cable, or do I need to buy different one?
no, apples, oranges.
Quote3. If I need to buy new cable, can anybody recommend which one to buy.
I would probably need between 80-100 feet of cable from antenna to the radio if I need to buy a new one.
yes, new cable. At 80'-100' depends on your budget. my recommendation would be 1/2" hard line but LMR 400 will suffice and be much easier to work with. I would suggest getting a a more accurate measurement and order it w/connectors installed.
JE -
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Huh. I thought one of the purposes of a dummy load was to prevent interference, especially at that far of a distance. Is there a device that accomplishes this?
remote base site @300' haat, we practically looked at it.
QuoteYes, it's called Faraday Cage.
It is very difficult to fully prevent cables, body of the radio, grounding wires, your body, from radiating. The higher the frequency the harder the task.
it was an open 20W 800Mc radio. we have never had a faraday cage at the shop. I did do work for a guy who had a nice one though. converted a small walk in freezer w/ grounded coper screen on the full interior and door. mostly did beepers.
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I notice the SMA female side of the adapter is not flush with the entire SMA male connector on the UV-5R as it does with an antenna... is RF escaping from this gap?
In a word, no.
QuoteI'm confused... I know a dummy load doesn't completely absorb or dampen all the RF that's pumped into it, but is it really typical for a transmission to still go that far?
funny story about that. I was tuning up a new channel for a customer on the bench (late 80's crystal TCXO) as they took some time to settle and the deviation had to be set also. radio is into a 100W dummy and was testing Dev on service monitor , boss gets a call that they are hearing everything I'm doing at the base 7 miles away.
go figure.
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was thinking tk 840 mobile. TKR 850/ 851 are 40/25
19 minutes ago, gortex2 said:It would be cheaper to add a PA to the TKR to be honest and clean way to do it. I run 2 of them for SAR work and its solid as a rock. Especially a 50 watt PA. They are out there.
agreed. get a mobile amp 5>50 and be done w/it
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you will need TOR low>PTT , RX aud> Mic Hi and as long as the ground is common. That should work but not 100% on it , its been a long time since I did something like this.
COR will key anything it hears that breaks squelch. Might need a pot and cap to fine tune the TX audio level.
Also as a side note an 840 should do 20W-25 W unless it's turned down -
7 hours ago, WRKC935 said:
You know,,,, the obvious... sometimes ain't so obvious.
Frequency spacing is my problem. Too close. For commercial, and even ham radio (density of used repeater pairs) you have to work with what you have.
GMRS.... NOTHING is assigned, nothing is fixed use. If you want to put a repeater up. You put it up. If you're a nice guy, you work with the co-channel users and either host them or assist them with reprogramming their stuff, but it's not difficult to work out a mutually agreeable situation with regards to repeater frequency pairs.
462.725 and 462.550 will fit in the combiner... and run 600 on another combiner.... problem solved
Epiphany in the shower this morning.
that is going to be tight. typical spacing is 250kC's unless you go to a hybrid combiner that has a typical loss of 6-9dB
550 and 725 still miss the mark by 75kC's
good luck, JE
How can I make my repeater allow APPROVED unit IDs only?
in Technical Discussion
Posted
Another option would be using an LTR controller ,w/that said all of your radios would have to be LTR capable