n4gix

Go to this site and do a search for the closest VE examiners in your area: http://www.arrl.org/find-an-amateur-radio-license-exam-session

Well, this is what's in my car currently. I have just enough room to tuck a Kenwood TK880 under the ashtray I think. I'll have it programmed with my local GMRS repeaters in one zone, and all other FRS and GMRS freqs in another zone. http://puu.sh/nPcQQ.jpg

Frankly I have both a UHF DMR radio and a dual-band 2m/70cm in my car. Between them, I am kept well entertained and rarely cannot find someone to talk to! GMRS is fine for local use as long as there are enough other GMRS users in your area and a decent repeater, but when traveling you'd mainly be listening to the sounds of dead silence.

If your friend is not a relative at all, then he or she would need their own GMRS license.

Yes, but quite honestly CHIRP is better suited for programming.

One would not use simple LOS alone, but when combined with the predictive model such as used by the Radio Mobile Online website, it is very useful. Note that RMO's calculations include topographical data, which is one reason why it might take up to two hours to plot a coverage map at the highest resolution! Just for fun, I plotted a hypothetical system based in Asheville, NC where I used to live. The surrounding hills created a lot of "shadows" that mostly blocked coverage until the antenna height approached 500' AGL. Professionals use much more sophisticated software when doing site surveys of course, but for us relative "amateurs" sites such as Radio Mobile Online are about as good as we have available.

Corey, line of sight (LOS) calculation is nothing but the math of physics. It is a geometrical formula that determines the distance at which the tips of the antennas have a clear, unobstructed path between them, assuming no other man-made or natural obstructions. The actual LOS could be much less, but never more! The earth is round after all. It would be so much simpler had the earth been flat... <snicker> Rather than bore folks with the complex math, here is a screen clip of an LOS calculator. I was a bit low because I was relying on my faulty memory. The actual LOS is more like 17 miles. Note that this assumes that the receiving HT or mobile has an average height of 6'. http://puu.sh/nNq9k.png Screen clip courtesy of http://www.hamuniverse.com/lineofsightcalculator.html Now LOS is not an absolute predictor of actual propagation distance, as your observations illustrate. LOS assumes nothing is in the way of the radio signal between the antenna and the horizon at a chosen height above ground. It does not take into consideration any attenuation caused by weather, band conditions, antenna gain, path loss, or other factors such as dB loss in coaxial cable. Likewise it doesn't consider any favorable circumstances such as signal refraction, reflection, or tropospheric scattering. Nonetheless, the physics and geometry do provide a solid basis for best case performance. By the way, the actual LOS calculated for your 150' AGL is 20 miles. So your "guesstimate" of 25 miles is reasonable. Keep in mind that the higher the repeater's antenna, the more it is likely to "shoot over obstructions". One neat site for generating a predictive propagation map is found here: http://www.ve2dbe.com/rmonline.html As indicated on the Radio Mobile Online website, it uses digital terrain information and a mathematical model to simulate radio transmissions between two fixed sites or between a fixed site and a mobile. The digital terrain information comprises three databases: ground elevation, land cover, and population density, which combined total 200 GB of information. Since the site is in French, a good English set of instructions may be found here: http://ham.stackexchange.com/questions/1921/how-do-i-make-a-rf-propagation-map-for-a-repeater Here is a screen clip from there for my repeater. I've been using this map as I drive around the area making tests. I've been very conservative in my estimates, figuring it's better to be surprised than disappointed... One thing is immediately clear from this. I really should have a more directional antenna with the azimuth aimed southwest. I'm "wasting" a lot of my system towards the northeast and the bloody lake! http://puu.sh/nNs9N.jpg

So the repeater was moved off the mountain? The antenna is at 100' AGL now? That will give about 15 miles LOS average.

I liked the first one well enough to order a second one. That should say it all. I use them mostly to monitor four specific frequencies of interest that I might otherwise miss when my scanners are scanning.

Corey, I have two of the UV-5RV2+ radios with Nagoya 771 antennas. They seem to be working fine for the few GMRS repeaters in my area. Oddly enough, even my MD-380 works quite well in analog mode.

Good grief! At the prices being charged at Amazon you'd think these were gold plated. Honestly you can find nice Kenwood TK-840 or TK-880 mobiles for around $50 these days, and even some decent HT's at reasonable prices. These are fully programmable and could be set up for both simplex and repeater operation.

I could still receive about 2 S units at the intersection of Calumet Avenue and US 30, which is about 10 airline miles from the antenna to my mobile's rear end. On the return trip with my car facing north, reception was about 4 S units. That's no surprise since that's where the major lobe of my trunk mounted mobile antenna will be found. With a limit of about 50' for the repeater's antenna, I had calculated about a 10 mile radius for 70% coverage. I still have some "weak spots" in the antenna system, not the least of which is a 20 year old lightning arrestor, and a 20 year old LM400 8' jumper from the arrestor to my desk. I've had to add another 6' of really shitty RG-58U coax with nickel-plated crimped connectors to reach the repeater's temporary location. Interestingly enough I was able to work the repeater from inside a Food-4-Less this afternoon on my MD-380 5 watt HT. That's about 5 miles airline from the repeater, from inside a large grocery store. I'm pretty confident that once I've replaced the lighting arrestor and the feedline into the office, performance should improve, especially on reception. In the meantime, I'm casting around looking for some prime "vertical real estate!" I wish I had my best friends connection (W9CTO). His 2m and 220 analog, and 440 DMR repeaters are sharing a receive antenna at 580' and a transmitter antenna at 500'. Talk about a H U G E footprint!

I was actually somewhat surprised, since $250 is about what I'd have charged myself... ...20 years ago! I'll be doing some preliminary range tests on my way to the LCARC monthly meeting in Crown Point, IN this evening.

Bill showed up this morning on time, quoted me $250, and I approved. Two hours later both the new Comet and Workman antennas are up and working. Unfortunately, the hardware on the middle (old) tripod was too rusty to be safely reused, so I had him put the Workman 2m/70cm on one of the chimney mounts. He took down a really old dual-band that had the top element broken off some years ago during a nasty storm. In the left picture you can see the unity gain J-Pole on the ground mounted mast. This is what the repeater's been using up until now. In the right picture from left to right, the Comet CA-712EFC (460-470), the "old dual-band", on the chimney forground is the new Workman dual-band, and on the far side is an old backup dual-band antenna. http://puu.sh/nD77M.jpg

Corey, tones are listed in the myGMRS.com entry. I've given up on finding anyone local to help install my antennas, so I'm waiting on a professional installer to give me a quote. He's supposed to call me today and arrange for a visit.

Yay! The 1/2" heliax was delivered today, along with a new roof tripod and 2x5" heavy steel masts sections. http://puu.sh/nzR1U.jpg

That will only work if the two radios have the same firmware version. I have two UV5Rv2+ radios with different firmware versions. I have to maintain two separate databases for them. Fortunately Chirp handles copy/paste smoothly!

The new Comet CA-712EFC antenna arrived yesterday and it is partially assembled and ready for fair weather to allow me to gather my "crew" together for an antenna party. The heliax was shipped separately and will not be delivered until Monday or Tuesday via UPS. If the specs are honest, this antenna is tuned to 460-470 MHz, 9.8 dBi gain... ...which is -if my math is correct- equivalent to 7.65 dBd which is pretty respectable still. (dBd = dBi - 2.15 dB) The antenna on the left in the other room is a Workman dual-band antenna to replace my nearly twenty year old one currently being used for my office 2m/70cm radio. http://puu.sh/nvQ0E.jpg

Well the new repeater finally arrived. I'm seeing a solid 45 watts out of the duplexer into a 50 ohm dummy load. I just got notice that the new heliax and antenna have been shipped. Hopefully they will arrive and I can arrange for my 'roof guy' to install them. In the meantime, it's running on my existing roof mounted high gain dual band antenna... http://puu.sh/nsGVe.jpg

Software license alone is $505 Bridge & Software license is $699

There are several GR1225 repeaters fully assembled available on eBay, for example this one: http://www.ebay.com/itm/Motorola-UHF-GR1225-Repeater-25-45-Watts-M44GRC90C2AA-444-474-MHZ-with-Duplexer-/291696338067?hash=item43ea74e493:g:QpMAAOSwPc9W06xW All it would require is programming & duplexer re-tuning. Cable and the CSS software are available with some due diligence. Same cable and CSS will be required for any M 1225 radios you buy anyway. For the record, this is not my listing! I'm only offering it as an example. You cannot "build your own" for $359...

My best friend has two of the 815-TG, and owns the VSWR bridge and software license. He told me he'd loan me his so I won't need to buy it myself. Aren't friends handy things to have? There is also an alternative method that frankly will work "good enough" using a Mini-Circuits ZFDC-20-5+ directional coupler. It's not a "one button solution" but will serve most people's needs quite well. See James Eagleson's video here: https://www.youtube.com/watch?v=X50qybdiLuk

Okay, after a lot of thought, here is what I've ordered tonight for the new Bridgecom repeater. I sure hope this works out well! 60' of 1/2" LDF4-50A and connectors should have ~1.36 db total loss. A really conservative estimate calculates that 40 watts into the system should put about 28.6 watts into the antenna. With 9db gain, that should be around 228 watts ERP. My new Rigol spectrum analyzer will be delivered tomorrow and the rest of the stuff I've ordered should be delivered by Wednesday of next week. I plan to do a full sweep VSWR analysis of the new antenna system before the new repeater is even connected! http://puu.sh/npaXv.png

John, I found that 1/2" regular heliax actually specs out to even lower loss than Superflex, and is a bit less expensive as well. A 60' length calculates out to 0.87 db loss. I haven't found specs for the connector loss but they shouldn't be too horrible. I'll have to use a N male at the antenna end, and a UHF male at the arrestor end. That should be less loss than a N male and adapter to UHF to match the arrestor's connection. I think for the time being I'll simply use the existing 6' length of LMR400 and use my new spectrum analyzer to do a sweep VSWR test of the new cable and whatever antenna I decide to install. I really only need about 45' where the antenna is now, but since I may be able to raise it up another 10' to 15', I'd rather have more "slack" than to have to patch in another section to lengthen it. I'm trying to decide betweek a Laird FG4507 7db gain @ $199.95 or a Comet CA-712EFC 9db gain @$129.95.

I have a new Bridgecom repeater ordered and am now thinking about replacing my existing antenna and feedline with something more efficient for a $1500 repeater! I was initially thinking about 1/4" Superflex heliax, but according to the specs I've found loss is around 4.5db/100' <Yikes!> The one major advantage is the 2" bend radius. Next for consideration is 1/2" Superflex with only 1.4db/100' loss. That's more reasonable I think. Price is $1.69/ft. The 5" bend radius is an issue though. The coax enters through a pass through tube below my desk, but has to make about a 2" bend and travel up the wall about 2' and then make another 2" bend to the back of the repeater's antenna port. What I'm wondering is if I could bring the 1/2" heliax down to my lightning arrestor, then use about 6' of 1/4" Superflex to bring it into my house, and if that would cause any serious issues. Alternatively I could simply use the 6' of LMR400 cable that's already in place. I'm somewhat challenged for height at the moment, so I'm thinking a 6db gain antenna would help compensate for the lower height. Any recommendations for antenna choice?