SteveShannon

Welcome to the forums. Only people in the Denver area are likely to be able to talk to you because of the distance limitations of GMRS. Your best bet would be to look at the map here to see what repeaters exist in your area and look at the clubs to see which ones are in your area.

You’re just a young guy! Before Tandy Radio Shack there was Allied Radio Shack and before Allied Radio Shack there was Allied Radio and Radio Shack, two separate companies. Allied Radio was a well respected competitor of Lafayette. Not everything sold by Radio Shack has been poor quality. They even sold some reasonable quality coax but they also sold some crappy coax as well. Personally I prefer to stay away from inexpensive coax. I would rather use quad shielded RG6 for UHF, even at 75 ohms, than some of the lossy 50 ohm cable.

I don’t recall ever saying that you are using the wrong coax. I pointed out that RG8x has a foam dielectric and RG58 has a solid dielectric and that’s why RG58 is frequently used for mobile installations. RG400 also has a solid dielectric and a tiny outside diameter. It’s expensive though. A person could build a Frankenstein cable using RG400 where needed and something with less attenuation elsewhere to make up the necessary length, but the splice points reduce reliability and potentially add losses. Also, nothing I’ve said has been demeaning or critical of you or in any way personal. I’ve tried to stick to factual information, demonstrating how I did any calculations.

Antennas typically consist of reactive elements and radiating elements. The reactive elements are used to match the impedance of the radio and feedline which is usually 50 ohms. The radiating element is one or more metal wires or rods that convert the signal into RF. It’s usually the most visible part of the antenna.

RG58 is used because the dielectric is solid and doesn’t deform like foam dielectrics, but you’re right that it’s even lossier than RG8x. Choosing cables for a mobile installation is a juggling act. The only cables that will withstand being pinched in a door are thin and stiff because of solid dielectric materials. But they’re also very lossy. So you minimize the length as much as possible and accept that they aren’t ideal.

I picked 10:1 as an example to demonstrate how SWR readings can be completely misleading when made through lossy cable, not as any assumption of the SWR of your antenna. Th right tests are important, but tests can be very misleading. If you want to know the SWR of your antenna, measure it at the antenna feed point, not at the radio. If you want to see how well your cable works, SWR of antenna and cable combination isn’t really an ideal test. Test the cable with a dummy load at the end. Test the SWR of the antenna separately. And put a power meter next to the antenna and then next to the radio and compare the results to see how much power is lost.

Those SWR numbers are not accurate. Keep in mind that SWR is calculated by the following formula: SWR = (Forward Power + Reflected Power) / (Forward Power - Reflected Power) But that requires an accurate measurement of the percentage of the reflected power compared to the original power output. At GMRS frequencies RG-8x converts 44% of the RF output to useless heat before it ever reaches the antenna. So of the maximum of 50 watts transmitted by a GMRS radio only 27 watts reaches the antenna. That’s the Forward Power. Then, if the impedance of the antenna isn’t perfect, some amount of the power is reflected back towards the radio. That’s the Reflected Power. By the time it reaches the radio 44% of the reflected power has been converted to heat. So, let’s say you have an SWR meter right at the radio and let’s also assume that the antenna truly has an SWR of 10.0:2 at 462 MHz. An SWR of 10.0:1 means 67% of the forward power is reflected. That’s a pretty abysmal SWR for any antenna. So for a 50 watt transmitter 33 watts reflects off the feed point of the antenna and back towards the radio. But now let’s introduce attenuation. 50 watts doesn’t really reach the antenna. We’re using RG-8x so only 27 watts reaches the antenna. Two-thirds reflects back towards the radio, so only 9 watts of power is radiated instantly. 18 watts is the reflected power at the feed point but of course 44% of that becomes heat due to attenuation. 56% of 18 watts, or 10.1 watts makes it back to the SWR meter. So the SWR meter sees all 50 watts forward power and only 10.1 watts reflected power. It’s calculation says that is a perceived SWR of about 2.6:1. The point is that lossy coax results incorrect SWR measurements, whether done by a nanoVNA, an expensive bench model Vector Network Analyzer, or the priciest antenna analyzer out there and seeing a lower SWR becomes meaningless.

That does make a difference, but what is the actual difference? How much of the difference is due to the antenna? Are the cables exactly the same length? Have you tested the insertion loss for each cable at each tested frequency? Remember, attenuation in an antenna makes SWR appear better. I believe these are the tabular results and I’ve arranged them by frequency It appears the older cable actually results in lower SWR for the 2 meter and 70 cm bands when connected to an antenna designed for those frequencies according to the value in the upper left of the screen. It would be interesting to see a single wideband sweep of just the cables into a dummy load to eliminate the effects of the antenna. Frequency Old Cable SWR -> New Cable SWR 462.000-470.000. SWR 1.900:1 -> 1.495:1 441.000-450.000. SWR 1.464:1 -> 1.498:1 151.800-154.600. SWR 1.888:1 -> 1.408:1 144.500-146.400. SWR 1.151:1 -> 1.395:1

Can you receive those same repeaters as well with the shorter antenna? You answered your own question.

Welcome, Zack!

There’s a very high probability that he has everything unlisted because he doesn’t want to allow anyone else on it. That’s his prerogative. Stalking him probably won’t make him more amenable to allowing you to use it.

Seriously, why not? They are not that much different to install than PL-259. In fact with these M&P connectors you don’t even need solder:

In only two characteristics is the PL-259/SO-239 system slightly better than the N connector: ubiquity and durability. A person can break an N connector, but it requires a certain carelessness. By ubiquity, I mean that I think I could find a PL-259 and SO-239 connector anywhere in the world. I don’t have the same level of confidence in the N connector anywhere. However, in every other conceivable characteristic, the N connector is superior, especially for UHF.

Yes, using cross tones/codes will work that way. I don’t know of any benefits to doing that, but yes. Anybody nearby, listening on 462.550 with no tones or codes, can hear anything that is transmitted by either radio.

Oh, no. You’re not getting off that easy!

Me too and I still owe you a beer!

I still don’t know what the length is, but rg213 still sucks for uhf.

You don’t mention the lengths of your RG-58, but for UHF almost any length is too much, but lossy cable like RG-58 will always make your SWR appear artificially low because less forward power reaches the antenna than passes through the meter so there’s less power to reflect AND much less reflected power reaches the SWR meter after reflecting from the antenna. So although the losses in RG58 is a problem, it’s not the cause of your SWR reading higher. Second, although a short or an open can be detected by a multimeter, the effect of RF frequencies is completely different. Yes, detecting a short would be reason to discard a connector or a cable, but resistive losses, the 002 (I assume that’s 2 millions?) that you measured are nothing to worry about. Without a dummy load and antenna/coax analyzer or nanonva your best option is to simply remove a piece at a time, replacing it with a known good component.

If the SWR doesn’t go back down when you remove the arrester, the problem isn’t the arrester. You either have a bad connector, cable, or antenna. Swap each piece out individually until you isolate the problem.

If you take the lightning arrester out does your SWR go back down?

Exactly what I meant by intercom.

Based on GrouserPad’s experience that’s not uncommon, unfortunately. There’s no reason to doubt your (or his) experience. TD H3s apparently arrive dead or die shortly after. Don’t waste time double checking yourself. Send it back, preferably for a different radio. You’re fine starting another thread but you would have been okay piggybacking on GrouserPad’s thread. Welcome to the forum!

There’s no way for it to get too hot except while transmitting. It’s the final output transistors that require cooling.

Have you tried VHT + TX? Doesn’t it only turn on the fan while you are transmitting AND the temperature is too hot?

I did.