Lscott

I have to get my wattmeter out and check mine.

If you look for the big names, Motorola-Kenwood-Icom, for example you can find a lot of used equipment. Myself I prefer Kenwood due to ease of finding the programming software, cables and documentation. When looking at used radios on any auction site, eBay, NEVER rely on the seller to post accurate info. I always look for the manufacturer’s brochures to see exactly what features the radio has. After that I look for the model number, and most importantly, the FCC ID number on the back of the radio. The brochures will list the radio models, on UHF, there are different frequency ranges, by their FCC ID. Now you know exactly what you’re looking at. If do buy a radio be sure the seller has a return policy. It’s possible to get a bad radio no matter how careful you check. I’ve got a few myself in a junk box. Also with the FCC ID you can look up the radio’s certification grants on the FCC database to see what services it’s licensed to be used under. Note newer radios likely will not have a Part 95(A)(E) certification, just Part 90. So far the FCC hasn’t bothered people using Part 90 certified radios on GMRS, but that’s no guarantee, so just consider it. While not Part 95 certified it is a current production radio. At the moment there are a number for sale on eBay. It will cost you a bit of money but you won’t be disappointed. I have several of them. https://forums.mygmrs.com/gallery/image/290-nx-1300duk5/?context=new

You could save a bit of money on radios if you can find a used commercial UHF one certified for Part 95A. The certification is still good under the new rules, Part 95E. These radios you can program in Ham 70cm frequencies and GMRS too. Then you only have one radio to carry around. A few of the old commercial radios, with Part 95A, can even do digital modes. However you of course can’t use the digital part on GMRS. Being able to do a favorite digital mode might be attractive on Ham while using the FM only mode on GMRS is a hard combination to beat.

Lead Acid batteries can still be unbalanced. The way the batteries, and cells in each one, are balanced is by over charging so the cells gas. That’s fine with liquid filled types. However you can’t do that with sealed types since you can’t add distilled water to bring the electrolyte level back up. If you let the sealed types gas they will eventually be destroyed. Also the charge voltage has to change with temperature. Good LA battery chargers have a temperature sensor you attach to the out side. https://batteryuniversity.com/article/bu-403-charging-lead-acid If you look at the data sheets for the sealed types you find there is a maximum charge rate specified which keeps the cells from gassing during charging. I’ve seen more than once people selling solar power generators at swaps with a 7 amp-hour gell cell, max charge current is typically 2 amps, in the box being charged by a 100 watt panel that outputs around 8 amps. Those batteries won’t last long.

The problem with series connected batteries is “balancing” them. Slightly different battery voltages can indicate a difference in the state of charge. Good battery systems use a “BMS” to keep all of the batteries well balanced during charging. The article at this link goes into much more detail about the various issues. https://www.allaboutcircuits.com/technical-articles/introduction-to-battery-management-systems/

I have the version that does all the digital modes, TDMA and FDMA. The amps were reviewed here: https://www.miklor.com/COM/Review_DMR-Amps.php The amp output falls off significantly on GMRS. I haven’t tested it with a wattmeter yet, however on the Ham 70cm band it draws about 5 amps on my bench DC power supply. On GMRS it only draws 3 amps. That suggests the output is only 60% of the “expected” 40 watts, basically 24 watts of output. If you have no other options than using an amp with an HT I guess you’re sort of stuck. However if you can, for the $100 the amp costs, I would just invest it in a quality higher power mobile radio.

That is a pain. However the few Kenwood NX-1300DUK5 radios I have allow me to assign a different radio ID per zone, and the radio can have up-to 128 zones. I can have different ID’s all dependent on what I need to do. The radios I have are the 400-470MHz band split. I can program in Ham repeaters in their own zones with my registered Ham DMR ID, and Part 90 frequencies, if necessary, with different ID’s in other zones without having to reprogram the radio. Very convenient. I haven’t run across another manufacturer’s models, outside of the new Kenwood ones, that allow this. Likely they exist, just I have seen any.

I’ve posted this a few times before. GMRS Digital Voice - 20221011.pdf

This topic comes up with regularly.

Leave it. Not worth the hernia trying to load it up.

Two big ones Eliminate the elitist attitude too many of the old hams have regarding those with a Tech Class License. There are Hams out there that won't even respond to a call that is a Tech Class. WTF? Same goes for Morse Code. There are those out there that remark, often, you're not a "Real Ham" unless you can pound out CW at 50 WPM. Sad.

I think most of us in engineering have had a professor like that at one point. It's not the wasted time copying down the worthless material I hated. It was suffering with writer's cramp doing it.

Can you spot the error in one of the formulas?

It's very difficult to do and get good results. The reason is the human body is part of the antenna system due to capacitive coupling between the radio's body and the users hand. I've tried it myself and discovered just how hard it is. Even a relative comparison between antennas isn't that easy either. Antenna Testing W9MDB.pdf HT-Antenna-Testing.pdf

A smart licensed operator and a properly tune antenna.

When I lived in an apartment years ago I had my Kenwood Ham HT modified. That allowed the reception of the common 900MHz cordless phones at the time. I picked various phone conversations but it wasn’t any good. Just about every one in range was from the Middle East speaking their native language. Rather pointless and boring to try scanning anymore.

Radio Shack sold such a radio back in the day. The guts of the radio was in the magnetic base, to comply with the fixed antenna rule. The controls were in a remote speaker mic that was run into the passenger compartment.

https://www.goodreads.com/quotes/14977-i-know-not-with-what-weapons-world-war-iii-will

Magnet mounts on 6M and HF don’t couple very well to the body of the vehicle. The cable ends up being part of the ground plane. On a 1/4 wave 6M antenna I ended up using a ferrite toroid near the magnet mount base to decouple the antenna. Otherwise moving the coax around resulted in significant SWR changes. I also paid a few bucks, at a flea market, for some magnet mount CB antennas, Little Wilson, with the idea of cutting them down for 10M. Finally gave up since the bandwidth was very narrow and the SWR jumped around every time I moved the coax a bit while adjusting the antenna.

If you kept your peanuts at least you can eat those.

For a one shot arbitrary pulse shape you can use the Fourier Transform to calculate the spectra. In a prior post I had a link for a paper that had the mathematical model for a nuke EMP for reference and testing purposes. The transform can be used to calculate the spectra. From that the parameters for shielding can be formulated. https://en.wikipedia.org/wiki/Fourier_transform

Or are, but just don’t work.

Another reason why many of the CCR’s, cheap Chinese radios, get a bad reputation.

That only works if you’re wearing a blue uniform with a shinny badge on it. Also it should be one of those huge leather Batman type utility belts with those hand restraints. Gives them crazy ideas.

I don’t agree with how he tests it at the end with a meter. It’s says nothing about the electrical connection. But the idea looks sound. My concern is tipping the can over and having something rip through the foil.