buying a good used GMRS repeater for neighborhood watch

[PastorGary]

If "IF" you find yourself in need of an antenna, I can recommend this one.  He also makes a dual band which is what I use.   Tell him the specific frequency you want it cut for and it will come to you with flat swr's.   I have two, GMRS and MURS and 440/2meters.   The GMRS/MURS is broadband enough I still get less than 2:1 in the 440 Ham bands, not so much in the VHF arena.   This one is a purely UHF antenna and more than likely what I am going to go with for my repeater when ready.  I has a good amount of gain as well.   Good Luck

 

http://www.ebay.com/itm/111026812813?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

 

 

As a side note, a half wave of the GMRS frequencies is roughly 1 foot or 12 inches.  I have always been told that jumpers should approximate 1/2 wave of the frequency you are testing for proper measurments.   I have also read that the same theory is used in tuning duplexers and the like.   I have never tuned a duplexer and maybe one of the more knowledgeable can chime in.  But it looks like your 1 foot jumpers were a good choice.  

 

 

+100

[Logan5]

ok, so i got the repeater working, however the duplexer seems to be one of the problems so I have TX and RX on seperate antennas and 2 seperate 30' run's of LMR400. it's got a buzz when transmitting and some how local digital transmissions on 462.600 breaks the ctcss set on my HT and blares out at the volume set. This is an annoyance that causes many of the people I need to communicate with to turn the volume all the way down. Since I have no way of changing the freq. or the pl code. I am stuck with this configuration, so I will be on the look out for a better repeater set up and send this unit to my brother who lives in the woods and less likely to get as much cross trafic and noise.

 

The unit I am looking at now is:

""Home Brewed" Motorola 30 watt UHF 2 channel repeater; repeater has two SM50 Motorola/Radius mobiles for the transmitter and the receiver; both radios are interfaced to provide repeater RX/TX functions; new fan installed on transmitter for cooling; total weight of repeater is less than 5 LBS; unit is capable of being powered by 12 volt DC either from a power supply, vehicle cigarette lighter or battery; included are a microphone,"

 

is a good price. does not include a duplexer, but is re-programable.

 

He also claims:

"all equipment certified/tested and programmed by a local Motorola Service Shop and I have a 30 day guarantee on performance; specs recorded when bench testing are 30 watts on TX and .25uv sensitivity on RX; we guarantee all equipment functions as specified or refund/replacement is allowed if necessary; many of these sold over the years with complete satisfaction!"

[JohnE]

you didn't post a price for the SM50 set up.

what I can tell you is that the SM 50 came in 2 power ratings 25W/40W I hope he is using the 40W turned down. the RX sensitivity is is typically .30uv. .25 is not a strech but I haven't seen too many Motorola'a do that out of the box and this radio is better that 15ys old, just sayin'. other than that they are pretty reliable radio, I have a couple myself.

a decent duplexer will runyou ~$200. I can't say how good the "cheap" duplexer's are on e-bay but I have heard that they have quite a bit of loss.

that said you should ask seller if he can provide a tuned duplexer w/setup. if he's saying its all tested and certed by a Mot shop I don't think asking for a duplexer would be out of the question. don't forget a pair of 6" jumpers too.

[Billy]

I would slow down at this point.  A good 1225 Motorolla tuned for GMRS freqs is around 500 on ebay give or take.  Your current machine has a fairly good reputation as a reliable system.   Maybe time to find a tech that can work on it, tune the duplexer and get it up and running rather than throwing good money after bad.   At this point I would ask the following questions;

 

1.  What is the area that you are trying to cover via HT (If we are talking a half mile or so a big repeater is not needed) Run predictions to see how many watts you really need with a good antenna at its current height.  You may find that you don't need a big system but are better off with a good antenna and a low wattage arrangement.

 

2.  I know you mentioned HOA but is this for the crew, the Neighborhood Watch or what.   Because duty cycle will figure in your choice.

 

What I am trying to say is if you are forming a neighborhood watch in a small gated community you don't need that much.   A system like the Ritron I just bought that does about 8 watts might cover such an area with ease with a good antenna.  That is what the majority of repeaters are designed for.  Think construction site, factory, cab company, etc. 

 

Anyway, ask questions before you spend too much money.  Slow down.   It can get expensive if you leap too quickly.  It is important to know the coverage area.   If it is small look at the low wattage repeaters from ICOM, Ritron and the like.   They both make stand alone, brand new programmed from the factory repeaters that are just plug in and 100% duty cycle for less then $1500.   That includes the warranty.  Bill 

[JohnE]

Bill has a point here.

what is your game plan and what do you need to cover?

[Logan5]

Question: The BUZZ I am getting on this Uniden repeater, is likley due to the power supply? since I have solar panels, should i consider powering it directly? I have 24volt mains, and the step down converters I have used on other 12 and 13.8 volt radios, were silent in operation. also, I have one user who when he transmits I only get a sound like a keyed mic 2 and 3 times but no voice from the repeater, just the open air sound with that meduimn level buzz. when he is close in it seems to work fine. when i am at his location, my radio has no problem reaching the repeater. so not sure what to make of it.

[Logan5]

yea, I don't want or need a 50 watt repeater, but something I can control and is better functioning. as this is also my Hobby, I am learning and enjoying the whole way. so even when I seem frustrated I am still happy to do something I love. as far as money is concerned I have a set aside for my hobby every month and ofcourse Paypal "Dangerous" allows me to Troll for "so called" Bargains on line. since i am also a ham I am not aginist operating a repeater in the 440 range someday. but in the mean time I am learning here first as you know "Old hams" can be very unforgiving.

[Billy]

Question: The BUZZ I am getting on this Uniden repeater, is likley due to the power supply? since I have solar panels, should i consider powering it directly? I have 24volt mains, and the step down converters I have used on other 12 and 13.8 volt radios, were silent in operation. also, I have one user who when he transmits I only get a sound like a keyed mic 2 and 3 times but no voice from the repeater, just the open air sound with that meduimn level buzz. when he is close in it seems to work fine. when i am at his location, my radio has no problem reaching the repeater. so not sure what to make of it.

 

 

If your radio works and his does not then it is his radio.   Quality in and Quality out!   But as far as the hum what type of power supply?   Battery is great and the cleanest, give it a try.   At least it will tell you if that is the problem.  Process of elimination!

 

Also make sure he is programmed for the wide band if that is what the repeater is running on. 

[Logan5]

all of the radios are set to narrow band. should I set them all to wide band, and try that? my double antenna tower on the roof is funny looking and the other half is giving me greif, can't wait to get back to a single antenna. I am not sure what to do in that area just yet.

[Logan5]

The power supply looks as orignal Uniden part, that fit's in between the radios. it sends power out the back panel to both of the radios, However the front control panal also has a red and white wire that connect's directly, I will take mesurments and see if it is also 13.8 volt's but I suspect it is going to be around 9 volts.

[Logan5]

Oh "JohnE" the Motrolla set is 229 shipped.

[PastorGary]

Logan 5 - Keep EVERYTHING in wideband mode including the repeater if that option is available to you.  GMRS is under Part 95 of the Rules and was NOT included in the narrowband mandate effective January 01.  Wideband will give a cleaner audio because of the bandwidth involved as well as providing more 'fringe' distance - portable to repeater.   IF the repeater is currently set to narrowband - like 11K0F3E for instance - and it is hit with a wideband input signal, the repeater audio may distort to a degree and will not provide clear audio on the output side.  20K0F3E is a much more user friendly format in general terms for GMRS. 

 

The buzz is probably from the converter or converters.  Some of those convert 12, 24 or 36 volts DC to 117 vols AC and then down again to another DC level - but have a SQUARE WAVE component rather than a nice clean 60 hz sine wave.  Some pieces of equipment will not operate on a converted voltage where a square wave was generated anywhere along the line.  Also, IF you are feeding a 13.8 VDC device with LESS than 13.8 volts, you will see the system straining to maintain frequency stability and may in fact be off frequency and that is where a possible FM phase noise is coming from on the output side. Make certain that the 13.8 VDC input is at the proper voltage UNDER LOAD (when the repeater is 'repeating') and that it is CLEAN  DC with no ripple from any A/C converting in the power generating system.

 

If you have 13.8 VDC at the repeater in standby and it loads down to under 12 VDC on transmit, the converter system does not have the power handling capacity that you need for reliable operation.  Does that repeater have a regular 120 VAC power cord on it to simply plug in to a standard 120 volt wall outlet or is is 13.8 VDC ONLY?

[JohnE]

to check this "buzz" since I can't hear it I'll have to guess as to what it could possibly be.

check voiltages and drop while keyed-if good

put a dummy load on TX side and see if you still have "buzz" if no one of 2 things - bad antenna or cable- not enough isolation TX to RX. you also might want to try the reverse of that too just to confirm. are your antenna's verticly or horizontaly isolated?

another possibility is........................................wait for it,

there is a repeater w/same frq/pl your using  although not out of the question but still possiblity

I don't know how urban or rual you are but in know on the frq I use in NYC it took me some time to get PL's that didn't key other machines. from my control point  there are six  I can hit cleanly and 2 have the same output tone.

[Logan5]

Ok, switched all the radios over to wide band, seems to work better so far. also moved the power supply around "since it's not secured" and buzz is now more of a Hum.

[JohnE]

bad filtering on the supply. try a different one and see what happens.

just curious PM me w/pl or e mail me some PL's if set too high will cause the same problem.

[Logan5]

Yes, JohnE, I am going to switch over to my batterys over the next few days.eleminating the AC power supply. Wide band is working well, a lil static, in addition to the Hum. but useable, I went to the beach earlier, and Keyed up the repeater close to 2 miles. mind you this is with a non optimal twin antenna set up. after I get a duplexer and or get this duplexer tuned. and stablize this set up, I will list it in the "With Permission" repeaters section. I have learned a lot of the past week. I decline to open an E-bay dispute, as this seller seems like an old guy much in my same situation, and I did end up geting this monster working. so I am satisfied. you guys have been awesome and of course YouTube for instruction. If any of you get to Fort Lauderdale, try to key me up my repeater and say Hi.

[Guest spd641]

Logan5,

If you have not bought the repeater for $229.00 checked by a Motorola technician let it go buy.I bought one several years ago and had nothing but head aches from it and also had a friend buy one a few weeks ago and it is not right either,programmed wrong CW ID doesn't work.The only reason the bought it was for amateur radio and it will not work in many different ways...William

[Logan5]

with careful antenna placement on my roof top mast. I am getting quite the range now. Several miles in most areas. still on 2 separate antennas. the UVS 200 is RX on top and the TX is now a Blonder Tongue Log periodic yagi, for UHF TV but seems to work quite well, I have a pre tuned duplexer I am hopeful will arrive tomorrow, so as to get the yagi off my mast. all and all I am happy with the Uniden repeater, but the seller should have been more careful shipping an item of this nature. I pulled the duplexer out of the unit and it is not tuned to the same freq. as the radio, I assume anyone that tuned duplexers would affix a new label or use a marker to update the freq. listed. and that has not been done. so I will look for a local shop that will do it. anyone know how much that should cost?

[Logan5]

with careful antenna placement on my roof top mast. I am getting quite the range now. Several miles in most areas. still on 2 separate antennas. the UVS 200 is RX on top an

[PastorGary]

In general terms, if a commercial radio shop does things correctly with a service monitor, the re-tuning should take 30 to 45 minutes of bench time.  It all depends upon what their hourly rate is and if they charge a full hour for anything UP TO an hour or not.

 

The local repeater tower close by is 197 feet above ground and the hill it's on is another 271 feet above the average terrain. It has a 50 watt output into a 15.6 db gain omni directional array and has coverage diameter of around 110 miles from mobiles. You don't have that much natural height in Florida so whatever you can squeeze out of it is a plus.

[Logan5]

Yep the tip of my UVs 200 is only about 37 feet, but is mostly unobstructed . when I move into my new house, I plan to get a 35 to 40 foot tower, but since i am always experimenting with antennas and different frequency's I am thinking a telescoping or tilt over tower as well. if i could use one antenna for everything it would save me much aggravation, but I keep hearing you need a dedicated antenna for the repeater.  I currently have 3 runs of LMR400 to the roof. RX and TX for the repeater and another for the antenna for my Handheld. and another question when they tune a duplexer is it so exact as the 462.675/467.675 or just 462.xxx/467.xxx?

[JohnE]

it should be exact. can you post a pic of the filter in question? also did you solve you "hum" problem?

a crank up tower would be nice but you still have to climb to cange antennas. I'm still in the process of putting somthing together for my machine at my house. looks like its going to be 50' of galv EMT w/guys. don't really want to get involved w/ree climbing.

 

 Gary, what antenna is that w/all the gain?

[Logan5]

"Gary, what antenna is that w/all the gain?" lol, I know right, I was thinking the same thing. sounds like a Yagi antenna.

 

Yes, I properly mounted the internal power to the chassis and the hum is almost non existent.  at this point I have rebuilt the interns of the unit, replaced the duplexer cables. my only problem seems when some users key up I can not hear any voice, even though I know they are talking, AlI I hear on my end is a mic being keyed over and over during that transmission,. perplexing.

[PastorGary]

(1) If "some users" still have their equipment set to "narrowband"  11K0F3E  - you may not adequately hear them on a wideband system.

 

(2) It is not a single vertical omnidirectional antenna... it is a stacked array.  I don't have a photo of the actual system... it's too high up for my camera to properly show detail. The system was installed commercially and it is somewhat similar to the system in this imaging below,  but there are three of these elements on tower top outriggers:

 

http://www.radiostructures.com/images/uploads/cdf450arraypic.jpg

[Logan5]

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