Lscott

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.

I don’t think that’s a good way to make one. You do need to use metal tape on all of the seams. Any break will allow leakage into the container. That also applies to the bottom too since that most likely is just crimped on with a small gap. Better than metal tape is use a small torch and solder along all the seams. Another poster mentioned a nested cage for the inner one must be isolated from the outer one. In the video that’s not the case. Not only that but the top of the inner cage is missing. I think if the outer bucket was prepared correctly that’s a good start. Then install an insulated liner. A second bucket prepared like the first is where you place your electronics. That bucket then fits into the first. Now you should have a good DIY double Faraday cage.

I purchased one of these simply because Kenwood doesn’t have one and looks like they have no interest in doing it either. I wanted a DMR radio. https://www.bridgecomsystems.com/products/anytone-at-d578uviii-plus-tri-band-amateur-dmr-mobile-radio

That’s what generally foils the whole idea not to mention repeaters, including cross-band types, are prohibited in MURS. A variation of the cross-band idea is an in-band spilt frequency operation. Many radios can be programmed to receive on one frequency and transmit on another within the same band using an arbitrarily frequency offset. The idea would require the GMRS user to transmit on a legal GMRS frequency and receive on a frequency in the Ham 70cm band. The Ham radio user would then transmit on a legal 70cm simplex frequency, which is programmed into the above GMRS radio for receive only, and receive on the GMRS transmit frequency programmed in the GMRS radio. Nether radio requires modifications nor dual band operation. Just the ability to program in spilt UHF frequencies with an arbitrarily offset. This operation in not legal either for the prior mentioned rules. The Ham station shall only contact other stations in the Amateur service. Also it could fall under the general prohibition to engage in one-way communications since the other station is NOT in the Amateur service. I wanted to point this scenario out before somebody dreams this case up and tries a convoluted argument this would pass under the rules. It won’t.

As a Ham you’re limited to ONLY making contact with other stations which are licensed and operating in the amateur service of the US, or of the country the station is located in. Obviously GMRS is NOT a Part 97 service. As a Ham you should know this. I would recommend you get a copy of Part 97 rules and throughly read it. It’s pointless to waste time on something you can easy research yourself.

The reason it’s done is the elimination of the heavy, bulky and expensive cavity filters required for an in-band repeater. This applies to analog radios. The filters are required because the RX and TX frequencies are close together. Without sufficient isolation the transmitter will overload the receiver such that it effectively become deaf. Remember the receiver is feeding every it hears to the transmitter at the same time. A cross-band repeater the frequencies are space far enough apart that a far simpler and cheaper filter can provide the isolated required.

It’s just not legal to operate this way on GMRS and MURS. That’s just the way the rules are written, like it or not. Some have gone and setup cross-band repeaters between MURS and GMRS anyway. NOBODY is going to guarantee FCC won’t come looking for you.

In theory yes. Legally no. On the Ham bands it’s done. In fact I helped a buddy install just such a system on top of an apartment building about a year or so ago. It cross-banded between the VHF 2M and UHF 70cm bands.

You absolutely must have the cable terminated using a load that has the same impedance as the cable. A good 50 ohm dummy load is perfect. The next best thing is a tuned antenna, where the SWR is under 1.5:1.

So far there are only two radios I’m aware of that can operate digital voice on the Ham 1.25m band, the Kenwood TH-D74 currently and the Anytone D578 mobile. The TH-D74A only does D-Star while the D578 does DMR. I wished Kenwood would have given the option to do DMR with the TH-75A. They likely couldn’t keep them in stock even at a $700 more or less price point. I get the feeling that DMR is slowing replacing D-Star. I talked to the Kenwood rep at the Hamvention last May asking why no DMR. He told me the offices here have been telling Kenwood Japan the same thing for a while, but nobody wanted to hear it in Japan. People that want DMR in a Kenwood radio have been buying their commercial radios. That’s why I own several. I’m surprised they haven’t figured this out yet. Wait and see Icom do it, maybe even offer both, then see how the sales do on the TH-D75. Kenwood isn’t stupid. They know how to do multi protocol radios. They do it now in their commercial lines.

I doubt it. The general recommendation is to ground yourself before handling sensitive electronics as a safety precaution. They make conductive wrist straps for that purpose with a coiled wire lead you run to the nearest earth ground point or conductive matt.

I don’t see why not. If nothing else it might increase the attenuation a bit from dialectic heating of the foam material at very high RF frequencies.

You really need to analyze everything after the radio as a “system” looking at cable losses and antenna gains. I did a simplified one for the antenna install I want to do on my Mazda. What you loose in the cable could be made up to a degree with gain in the antenna. See attached files. Diamond C110 Extension Cable.pdf Diamond C101 Cable Assembly.pdf Diamond K550 Luggage Rack Mount.pdf Mazda 2023 CX-5 Antenna System Analysis Rev 5.pdf SG7500A.pdf CA-2x4MB Manual.pdf https://forums.mygmrs.com/gallery/image/282-ca-2x4mb-scansjpg/?context=new https://forums.mygmrs.com/gallery/image/283-sg7500a-swr-scans-2jpg/?context=new

This is the kind of info that’s useful.

I have a few thoughts on that. While a lot of criticism was leveled at the government for waiting to shoot it down over the ocean there might have been a legitimate security reason for it. Getting photos is one thing, but I think the main purpose was to monitor our military communications systems and gage our response procedures and times to an unknown threat. If China invades Tiawan that would be very valuable Intel. Waiting until it was over the ocean to respond sort of wasted their efforts in that area.

It’s the high altitude air burst are the dangerous ones for EMP. https://doh.wa.gov/sites/default/files/legacy/Documents/Pubs/320-090_elecpuls_fs.pdf

https://www.wearethemighty.com/mighty-history/the-first-time-the-us-tested-an-emp-weapon-was-a-doozy/ A lightning strike is not the same as a nuke produced EMP pulse or a solar flare. However it can exhibit similar effects. The main effect is the high electrical field intensity in volts per meter. For nukes that could be in the range of thousands of volts per meter. https://www.energy.gov/sites/prod/files/2021/01/f82/FINAL HEMP MEMO_1.12.21_508.pdf