Lscott

Some people seem to have a hard time grasping the idea of a frequency offset between TX and RX and can't get into their local repeater either.

It gets a bit more confusing when you include gain antennas in the mix. For example with a simple 1/4 wave antenna lets say your S-meter reads 2 S-units. Then switch over to an antenna with 6db of gain now your S-meter will read 3 S-units. Nothing on the TX end or path changed other than your antenna.

Ah, a proper FM demodulation circuit includes a limiter stage designed to deliberately remove any amplitude changes, before the discriminator stage, so it response only to the frequency deviation. For good discriminator performance there has to be sufficient signal amplitude to achieve full limiter action. https://www.arrl.org/files/file/Technology/tis/info/pdf/8506025.pdf

Anyway back on topic here. I did an analysis of an antenna system I want to install on my new ride. I had a choice between several different cable types and lengths along with antenna and mount. I wanted a roof rack type mount so the antenna had to be a 1/2 wave type that doesn't require a ground plane. The goal was to see which combination was the best case compared to what I can get to fit. I have to route the cable around a tail light assembly and it has to be behind the rear hatch. It's a very tight fit for the cable and I'm not into drilling any holes. I went a bit overboard with the analysis but gives you an idea what things to consider. For example some of the cable loses can be made up, sort of, with a higher gain antenna. That's one of the trade offs you can make. It looks like what will work is the short coax cable mount, using RG-316 thin coax cable, with an RG-8 mini cable extension. Keeping the mount with the RG-316 coax cable length short makes a difference. The mount using RG-58C is a bit better but the difference wasn't more than a few percent different from the one I think will fit best. If range was ONLY a function of power then the range change varies as the square-root of the ratio of the powers. I calculated a likely range change based on the square-root of the ratios of power loss/gain between the different configurations. One point about the cable connectors. They are all RG-8 mini type, including the one on the end of the coax cable used on the mount. It comes with a RG-8 mini to PL-259 adapter. The RG-8 mini adapter is a constant impedance type, the normal PL-259/SO-239 are not, thus there is likely to be little in the way of SWR issues using RG-8 mini through out the system. The adapters are rated up to 2.5GHz and the insertion loses are very low. Diamond C101 Cable Assembly.pdf Diamond C110 Extension Cable.pdf Diamond K550 Luggage Rack Mount.pdf Mazda 2023 CX-5 Antenna System Analysis Rev 5.pdf SG7500A.pdf Coaxial Cable Attenuation Chart.pdf

Just a comment here about power verses range. Most of the remarks in general are true in favorable conditions. However where power may be a significant factor is in fringe conditions. I'm not talking about at the limit of operating range. I'm thinking more along the lines of cases where signal attenuation could be high. Examples operating in heavy foliage areas, heavy rain, inside of building with radio wave absorbing materials etc. I don't see much in the way of usage experience mentioned under those conditions.

I was at a local Ham swap this morning and yup I saw one guy with a couple of radios complete with speaker mics hanging over both shoulders.

You can never have too many radios. There is always going to be some feature or function you want on your "favorite" radio but doesn't have it. Then you see it on another radio. Soon you start thinking about buying it. You can spot a radio geek by the number of radios hanging off their belt. Most likely they have more than one.

It’s been a long while, starting to stink a bit now.

Not to mention cross banding between MURS and GMRS you’re going from an unlicensed service to a licensed one. The FCC definitely won’t be pleased.

That's possible. Look at the Kenwood NXDN radio brochures attached. These are the radios I have. The IS models show as 5/1 watt. I got two UHF radios from Canada a while back, both were IS models and both had very low output power. The Canadian brochure shows no more than 2 watts for the UHF models, bummer. I had to send both radios to a particular shop that was certified to work on Kenwood IS rated radios. I couldn't send them just anywhere. They set them for the expected 5 watts, for the US market, and still kept their IS rating. NX-200_300IS.pdf NX-200_300 Canada.pdf

Be careful of the "intrinsically safe radios" since part of the specifications has the output power reduced for operation in explosive environments in some cases. I've seen nominally rated 4/5 watt radios set for 1, or maybe 2, watts at the most. If that's what the radios are set for then you either need the equipment to re-calibrate them or spend the bucks sending the radios in to a shop. I've been there and done that a couple of times, expensive, $120/hour bench charge minimum, $20 shipping each way and $8 insurance.

I would research those radios a bit more. They come in different band splits. Often the seller gets the info wrong. I always try to get the FCC ID and look up the frequency split the radio has the grant just to be sure. I don't know if the Icom radios will operate outside of the official band split. In your case I would likely go for the 400-470 one. That covers the whole Ham 70cm band, GMRS and most of the commercial band frequencies. A few other things, make sure you can get the radio to do wide band FM, and most of the older Icom NXDN radios will only do the 6.25KHz digital NXDN protocol. I heard the new Icom radios might do both 12.5KHz and 6.25KHz NXDN. I know all my Kenwood NXDN radios will do both. As far as software goes I don't have any. You might get a copy from this link. If you haven't registered before you get points for signing up. I think you will get enough to qualify to download the software. https://hamfiles.co.uk/index.php?page=downloads&type=entry&id=radio-programming%2Ficom-programming%2Ficom-cs-f3160-f5060-rss Now if you want to buy it then try this link. https://www.buytwowayradios.com/icom-cs-f3161-f5061.html If you do want to bid on the radios make absolutely sure they are NOT password locked!!!! I had that happen with a few Kenwood radios. Fortunately I had the special "engineer" cracked versions of the software that allowed me to bypass the damn read/write passwords used on them. Those were sort of hard to find. One I had to get the cracked software from a source in Mexico of all places. IC-F3161_4161.pdf

I've got a few of the TK-270G's and TK-370G's too. I just looked for battery packs on eBay. Make sure the seller has a money back guarantee. The cheapest ones are the KNB-14, but have the least capacity. Another option is an AA-cell battery holder. https://www.ebay.com/itm/314150918381?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=3jJIioNETiu&sssrc=2047675&ssuid=j_t98fioS_6&widget_ver=artemis&media=COPY You can then buy some of the Eneloop cells to fill it. https://www.panasonic.com/global/energy/products/eneloop/en.html And lastly you can check these guys out. Not the best prices around but have a good selection. I think the KNB-15AH and KNB-15A will work. https://batteriesamerica.com/collections/land-mobile-radio-kenwood-batteries https://batteriesamerica.com/collections/land-mobile-radio-kenwood-batteries/products/knb-15a https://batteriesamerica.com/collections/land-mobile-radio-kenwood-batteries/products/knb-15ah

Judging by what you see in those key-down videos the people there are well past the point of having to worry about it.

That’s about right. The mounting pole acts as a reflector for the elements giving a bit of directivity to the array when they are all mounted on one side. If someone is looking at this type of antenna they should keep the above in mind.

Yes it would. Another poster, gman1971 I think which I haven't seen posting in a LONG while, talked about putting up a 4-bay vertical. I was curious how it looked from a coverage point of view since he said it was directional. I simulated to see. It does have some directivity but it's not huge.

I tried to simulated a solution like the above but used just two simple vertical dipoles. Since it has to do with antenna modeling, there is another thread on the topic, I put the results there and a link to it here. https://forums.mygmrs.com/topic/5218-modeling-small-handheld-radio-antennas-and-a-very-brief-primer-on-the-science-behind-the-range-we-get/#comment-52100

This is part of another thread dealing with the possible access of a US located GMRS repeater by unlicensed GMRS users in Canada. Its another response to the following post. https://forums.mygmrs.com/topic/5213-cross-boarder-usacanada-gmrs-communications/#comment-52029 This is the repeater in question and the approximate coverage zone. https://mygmrs.com/repeater/6815 It got me thinking is there a simple way to do it without having to use Yagi antennas. The answer seems to be yes. I'm putting the results here since it really shows how the power of antenna modeling can be used to answer some basic, but important questions, to solve real problems. The simplest idea is using two "phased" 1//2 wave vertical dipole antennas spaced apart on a boom and rotated to the desired angle. You get a cardioid pattern where the "null", back side of the cardioid, can be place along the US-Canada border while still covering most of the intended targeted US coverage zone. It doesn't reduce the signal to zero but likely enough it won't prove attractive to bother with unless the station is very close by. The software used here was EZNEC.

I think that’s where I took my exams years ago.

The other modeling software I use is EZNEC. https://www.eznec.com/ In any case modeling antennas is a great way to get a feel for what is going on. Now testing small HT antenna is something else!

There are only 8 repeater frequency pairs available with the usual 5 MHz split. Two are not usable in this area due to Line-A. So out of the remaining 6 there are 4 used by one old and 3 new repeaters leaving 2 left. Out of those 4 there are 3 with a wide, 20 to 25 mile, zone coverage range. After they're gone, the currently unused frequency pairs, then the fun starts with trying to mitigate interference issues with additional repeaters.

I agree. In that case he would be better off looking for a good used or new commercial grade radio. Unfortunately they are almost universally mono band radios so he would need two, one each for VHF and UHF. The upside to that is with the right frequency range, typical range is 136 MHZ to 174 MHZ, the VHF radio will handle all of the 2M band, MURS, railroad FM, marine and NOAA weather frequencies. On the UHF side a frequency range of 400 MHZ to 470 MHz will cover the full 70cm band, GMRS and most of the commercial business band frequencies.

Actually there are now 4 GMRS repeaters in the Detroit area. Of course all above "Line-A".?

If you’re looking for a “cheap” radio the TYT TH-350 is a tri-band, 2M - 1.25M - 70cm, type. It can be opened up for GMRS. It uses the Baofeng type programming cable and microphone accessories. Just be aware the radio is NOT Part 95 certified if that matters. https://store2.rlham.com/shop/catalog/product_info.php?products_id=74359&osCsid=gsc5lupm4qgc3dnoijn4go3o27 The other radios mentioned will likely work better but are going to cost more. You get what you pay for.

You should see my HT collection. I have a pic in my photo gallery. Once you look you’ll see why I’m interested in the wattmeter.