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Author Topic: How to Build a VHF Repeater?  (Read 6798 times)
KB3DSC
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Posts: 21




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« on: March 25, 2005, 09:08:07 AM »

I have had my license since 99. My friend is getting ready to take his exam soon. We would like to build a VHF repeater. He works for a communication company so getting parts is not going to be hard. I would like any input on how about building a repeater. I've been told some of hte things i need, radio, antenna, controller etc. However all the web sites I have seen online have been quite vauge. We are trying to go inexpensive right now because we only want this to cover a small area. We will probably hook up an interface to connect it via EchoLink as well. If anyone could email me some info, web links, pictures etc. I would be very grateful. Thanks.

73

Brian (KB3DSC)
bkeefe@verizon.net
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KZ1X
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Posts: 3227




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« Reply #1 on: March 25, 2005, 09:18:18 AM »

FIRST thing you need is a coordinated frequency pair.

You CAN NOT put a repeater up unless you first have a coordinated pair, from the local coordination board for your area.  You will need detailed information about your repeater site such as its latitude and longitude, heaight above sea level, height above average terrain, and some coverage plots (see if you can get your local cell site engineer to run these for you with their software)

2nd:  visit  http://torborg.com/ka2dew/catfish.htm
(or the Google cache of it if the server is down) for a story about what you are planning to do

3rd:  in virtually every area of the country, there are many, perhaps dozens, of idle repeaters ... why do you want to put up another repeater?
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KE6PKJ
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Posts: 256




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« Reply #2 on: March 25, 2005, 10:00:08 AM »

Hi Brian,
See www.repeater-builder.com/rbtip/ for everything you'll ever need to know. In reality you don't need to have a coordinated frequency pair, there are lots of uncoordinated repeaters operating. It is however a very very good idea to obtain coordination, so you're not unintentionally interfering with anyone else.

I understand your need to build something like a repeater  to feel the accomplishment of your skills, hard work and energy. But like Steve said, there's tons of unused repeaters sitting idle. Why not build a repeater up at 900 Mhz or 1.2 Ghz? That frontier is still available and your cavities and antennas will be much cheaper, plus you'll be hard pressed to find two vhf channel pairs available.

Good luck,
Kirk
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N3PAQ
Member

Posts: 82




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« Reply #3 on: March 25, 2005, 10:21:58 AM »

My Reply won’t be much help, but when I read about putting up a 1.2ghz repeater, a light bulb went off in my head, that would be a great project.  Then I thought about the number of 1.2ghz transceivers on the market today, I think there are only two, the IC-910H with the UX-910 23cm Band module, and the Kenwood TS-2000X.  I think there are some others you can get from Japan.  With that in mind, I think there would be just one more idle repeater hanging around.

Putting a little more thought into it, perhaps a 70cm ATV repeater would be a better project.  Don’t get me wrong, I would love to see 23cm become the new 2 meters, but there just doesn’t seem to be a market for it in the amateur community.

N3PAQ
Joe
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N8UZE
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Posts: 1524




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« Reply #4 on: March 25, 2005, 12:16:22 PM »

Comments:

Repeaters on other than 2m:  It is the chicken and the egg syndrome.  However, the existence of the repeaters would help feed an interest in radios with these capabilities.  

Coordination:  While highly desireable, it is not mandatory.  The kicker though is that in a dispute between the coordinated repeater and the uncoordinated repeater, the rules side with the coordinated one.  There are parts of our country with such wide open spaces and low population densities that there are plenty of frequencies available.
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NJ1K
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Posts: 320




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« Reply #5 on: March 25, 2005, 04:52:44 PM »

Building a 2 Meter repeater is a worthy project and loads of fun even if it never becomes heavily populated...Go for it and enjoy soaking in the knowledge and experience... I have built a few and here are a few caveats:

There is nothing in the rules that REQUIRES coordination however, I would recommend contacting your local frequency coordinator and see what's available for your location... This service is free and he will (should) help you with the details... Before you call him, get a GPS coordinate reading on your proposed site...  He will need that...

There is nothing inexpensive about building a 2 meter repeater (unless you have access to duplexers, controllers, connectors, service monitors for free)....

UHF and up is much less expensive but there still are lots of unforeseen costs...

The easiest was is to obtain a good quality controller and 2 identical surplus commercial VHF radios (motorola, GE Ericsson, etc) and use one for the transmitter and one for the receiver... These can be had at places like ebay or ham fests for $5 to $25 each... Pretest both radios first to make sure they work well..  Tune them up for your proposed frequencies (preferably on a service monitor/spectrum analyzer).... Wire them into the controller as per the controller manufacturer's instructions... Connect the transmitter to a dummy load and start it up and set all the audio levels per the controller manufacturer's instructions.... Once it's working and stabilized, you are ready to hook it up to you duplexer and make final adjustments....

OOPS, don't hook it up yet... You need to tune your duplexer first.... For this you SHOULD use a spectrum analyzer with tracking generator or a service monitor however, there are ways to tune duplexers to an acceptable standard if your repeater is very low power (less than 20 watts).... You can tune it with an HT, dummy load and watt meter...

Duplexers for 2 meters will run somewhere between $400 and $1000 used at places like ebay... Don't make the mistake of buying a "compact mobile duplexer" for cheapo... These will not provide the isolation you need for the narrow 600 kHz split that 2 meter requires... You need a serious full size cavity duplexer to do it right... Certainly there are other homebrew ways to build a duplexer but it likely will not work unless you have a serious spectrum analyzer for testing, tuning and adjustment... These cost about $20,000 new and about $5000 for a GOOD used one...

FInally, you want to use a high quality antenna with low take-off angle and high gain... Also be sure to use VERY low loss coax (preferably hardline).... And be prepared for sticker shock when you go looking for coax connectors for hardline,,, hehehe....

Again, it's a fun project and you can learn loads of stuff that you would never be exposed to without actually doing it yourself... After you build a couple of 'em, you gain lots of confidence with repeaters....  If you used high quality components with surplus commercial gear and a good used duplexer and a quality controller, you will sink about $1000 into the project but you will have a REAL repeater that sounds great....

One more note:  If you plan to install it in a remote location, you will need a secondary (auxiliary) control link to control the repeater (phone line, 220 mHz or 440 mHz receiver, etc. per FCC part 97)... DOn't be mislead about controlling your repeater on the input frequency... Automatic control REQUIRES an auxiliary control link....

To give you an idea of the last one I built:  I used a pair of GE Ericsson Delta SX programmable radios, a CAT controller and a Wacom duplexer with a third Delta UHF radio for the control link... The radios required NO INTERNAL mods... All the mods were done in the wiring harness by using 3 surplus control cables... The radios slide into a rack mount shelf stacked one on top of the other and can be disconnected and pulled out for service in a minute... Spare radios can be tuned up and left at the site in case one breaks down... The receiver came stock with a preamp built in... It can put out up to 110 watts but can be turned down to about 25 with no difficulty...

There are lots of other commercial radios out there that can be utilized the same way... But I would stay away from using regular ham gear such as Yae-Com-Wood stuff... It doesn't have adequate shielding and durability for repeater duty not to mention the poor audio quality...  

Repeater-builder.com seems to be the most extensive web site for what you want to accomplish... I gained tons of important info there... Particularly, read and READ again and again, all the articles on duplexers... The duplexer is what puts the magic into repeaters...

Good luck on your project and come back with a progress report....

73 de NJ1K

P.S. Don't forget lots of shielding on ALL cabling and connections... Very important with repeaters....
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N3PAQ
Member

Posts: 82




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« Reply #6 on: March 25, 2005, 05:15:03 PM »

NJ1K - that was a quality answer - I'm thinking, a lot can be learned when building that vhf repeater, and that know how could be later applied to that 1.2 GHz repeater, which will probably be a little more complicated.

Thanks,
Joe
N3PAQ
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NJ1K
Member

Posts: 320




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« Reply #7 on: March 25, 2005, 05:37:33 PM »

I think the problem with 440 902 and 1.2 gHz as far as popularity goes is that these bands are a little "too" much line of sight for the practical ham's comms needs... 2 meters holds it's popularity because it has fewer band openings than 6 meters and the wavelength is short enough to make it practical for mobile, handheld and repeater applications... On the flip side, 440 is great for comms inside of buildings as 440 penetrates concrete and other building materials better than any of the other bands....  Also, 440, & 902 make great linking bands for linking several repeaters together (line of sight, small equipment, smaller cost)...

For general local comms though, I prefer two meters for performance as well as popularity...

I work ARES a lot and find that there are still lots of people out there who don't own any UHF gear but EVERYONE has two meter gear....

In short, yes there are loads of two meter repeaters out there but more is better (so long as interference issues are kept in check)....
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WA4PTZ
Member

Posts: 528




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« Reply #8 on: March 26, 2005, 04:42:25 AM »

Ditto to KZ1X...before you purchase any equipment
it is wise to have a frequency pair. You may want
to look at 440, 900, or even 1200 rather than 2
meters. The 2 meter pairs are generally rare. An
another item you will want to research is "Frequency
Coordination". It is required, and it is important
to find out who handles your area. If this is your
first venture into repeaters you have a lot to learn
before you are ready to build one. There are some
very good repeater newsgroups and reflectors out there
which can answer many questions. Repeaters are not
"plug and play".
73 and good luck,
Tim
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KB3DSC
Member

Posts: 21




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« Reply #9 on: March 26, 2005, 06:32:20 AM »

I want to thank you all for your responses. It has been very helpful. I think we are leaning towards a 440 now. We received a GE UHF Rangr. So we may use that. Also its possible to get a GE Mastr II UHF. There is a few 440 repeaters in our area, but not many, plus it seems that they are a little cheapier to run. Thanks again. Anymore input will still be appreciated.

Brian
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K7VO
Member

Posts: 1010




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« Reply #10 on: March 26, 2005, 10:50:22 AM »

For Joe, N3PAQ:

I used to own a 23cm repeater which did get some use.  If you build it they will come, particularly if you are in an area with no 23cm repeaters.  A lot of people have multiband gear with the band in it.

There are (or have been) lots of 23cm rigs made.  It's the #1 repeater band in Japan today.  You can find some amazing stuff on the used market. Some examples (by no means a complete list):

HTs:

Icom IC-T81A (4 bands)
Icom IC-Delta1A (3 bands)
Icom IC-12GAT
Kenwood TH-59AT
Yaesu FT-911
Yaesu FT-104

Mobile:

Icom IC-1200
Icom IC-120
Icom IC-3700 (70cm/23cm)
Icom IC-Delta100H (2m/70cm/23cm)
Icom IC-901A w/UX-129A module (up to 6 bands)
Kenwood TM-742A (w/module, multiband)
Kenwood TM-741A (w/module, multiband)
Kenwood TM-842 (70cm/23cm)
Kenwood TM-841 (70cm/23cm)
Kenwood TM-942 (2m/70cm/23cm)
Kenwood TM-941A (2m/70cm/23cm)
Kenwood TM-541A
Kenwood TM-531A
Kenwood TM-521A
Kenwood TR-50
Kenwood TM-2400 (23cm/13cm, w/module)
Yaesu FT-2312R
Yaesu FT-2311R
Yaesu FT-6200 (440/1.2GHz)

Base:

Icom IC-910H (as you mentioned)
Icom IC-970H
Icom IC-1275A
Icom IC-1271A
Kenwood TS-2000 (as you mentioned)
Kenwood TS-790A
Yaesu FT-736R

Yes, some of these are strictly on the used market, but some of those can be had inexpensively.

The problem isn't lack of equipment in the hands of hams.  Lack of repeaters and lack of promoting them is a problem.

BTW, if anyone as a UX-129 module for my Icom IC-901A you can e-mail me as I may be interested if the price is right.  A mobile unit or two (old IC-120s, if inexpensive, are fine) would be nice.

73,
Caity
K7VO/8
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N3PAQ
Member

Posts: 82




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« Reply #11 on: March 26, 2005, 12:05:34 PM »

K7VO,
After doing some reading last night, I realized that you can still buy the Kenwood TM-541A new, but none of the big ham vendors list them for sale.

I think you are right that it is a lack of repeaters contributes to the inactivity of the band.

I think I'll start a thread on this on VHF/UHF.

Joe
N3PAQ
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WA2DYA
Member

Posts: 43




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« Reply #12 on: March 26, 2005, 06:33:30 PM »

The most important consideration for a good working repeater is its site.  You need 400 ft of height above the average terrain.

After that, an xmit power level in the 50 watt range, a receiver sensivity of about 0.2 microvolt, a properly tuned duplexer and 6-10 db of antenna gain will provide really nice coverage for mobiles out to 25-30 miles.

I have found that repeaters that operate above 2 meters need extreme attention to all details for satisfaction.

---  CHAS
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K4III
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Posts: 206


WWW

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« Reply #13 on: March 31, 2005, 09:04:10 AM »

3 most important factors:

1) Money / Cost  
2) Antenna Height  
3) Frequency Availability

VHF:

-Duplexer Expensive ($400-1.5K used)
+Cheaper Coax Alright (RG-8 <100ft will work)
+PL-259s will work (but not recommended)
+Antenna Heights (50-150ft about 10 mile radius)
-More Interference potential (Ham 600k split)
+More Wide-band equipment available
-preamp only allowed with added filters
+preamp not always needed
-Availability of 2m ham frequencies
+Almost all radios have Vhf
-Total cost of project from used equip min.$1500

UHF:

+Duplexer Cheap ($50-300 Used)
-Better Coax Needed (Heliax/Hardline >50ft)
-Antenna Height (200-2K ft needed for 20+ mile radius)
+Less Inteference potential (Commercial 5Mhz split)
-Better Cabling Required / N Connectors a Must
-Pre-amp almost always needed
+Preamp doesn't always need added filters
+Availability of ham frequencies
-Not all radios have uhf
+Total Cost of project from used equip min.$550


Total cost figures are cost incurred on 2 systems I personally placed on the air and do not include the controller costs. Controllers can start at $50 for kits to over $1K for advanced high-end units.

Good Luck!

Jon
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