Lscott

Oh, you’re right about the smell test. Remember he’s trying to sell these to less technically sophisticated people. All that crap about testing might be true at one point, maybe while he did the initial testing, but I’ll bet it’s just there to convince people to pay $25 for adapters he buys from a Chinese source at $3 each in bulk with a 10 cent strip of sticky sided copper foil to make the ground connection.

Yes the stud is hot, but it's not running to the chassis. I use a very similar adapter for my two Kenwood TK-370's that use this type of antenna connector. You'll notice the stud is isolated from the connector shell in the photo. It goes through it to the center pin connection for the BNC socket on the other end. The other photo shows the stud type antenna connector on the radio. In this case you'll notice the stud screw hole is also isolated from the slotted ring nut. When the adapter is screwed in the shell makes contact with that slotted ring nut which happens to also be the ground side of the radio. It looks like in the case of the 7550 that ground connection is stuck behind the plastic case so the guy had to run a copper foil strap from the back side of the radio, the mounting screw for the belt clip, up to the edge of the antenna socket well. When the adapter is screwed in the shell makes contact with that strap completing the ground connection between the coax shield and the chassis ground. The adapter he uses is likely very much like the one I use.

I think that's because there is no "ground side" to the coax. That's always been the warning about using these antenna stud type adapters. The link below shows how that problem was sort of worked around. https://alfonsofaustino.blog/2019/09/23/alfonso-faustino-motorola-xpr-7550e-external-antenna-adapter/ Scroll down to the photo of the top of the radio. You'll see a copper foil ground strap. When the adapter is screwed into the stud the "shell", the knurled part, make contact with that copper foil. The copper foil is run down the back side of the radio to the mounting screw for the belt clip. That screw goes into the aluminum chassis of the radio which is the ground side for RF, the "ground plane". It's a kluge but if it works reasonably well the advantage is no modifications to the radio are required. The guy selling the adapter doesn't show what is going on with that copper foil strap, and very deliberately talks around about what it does exactly, which is his whole secret to getting it to work. Once you figure it out you can likely buy these stud adapters for less that $7 or $8 then use some of that conductive aluminum foil tape you get at the hardware store for sealing heating ducts in place of the copper foil. Should work about as well. The two Kenwood radios, that I have with a stud type antenna connector, has an exposed slotted ring nut around the stud, where the stud itself is isolated, sits in a Teflon bushing, and the stud is grounded to the radio's chassis. Screwing in an almost identical adapter it makes contact with the radio's ground and thus the shield side of the coax.

Kenwood used a stud type antenna connector on their TK-270/370 HT's, not the newer TK-270G/370G models which are the typical reverse SMA type. I have an adapter for stud to mate with a BNC terminated cable. Fortunately the way the stud connector is built in to the radio the slotted nut around the stud, the stud is isolated by the way, is exposed. When the adapter is screwed in the adapter's flange part makes solid contact with the flange nut for the shield side of the coax connector.

Bummer.

Interesting there is an SMA option. That suggests one could order the part(s) and retrofit the radio with the other connector type.

I have a FT-817. One disappointment with it the upper end on VHF is 154 MHz so no weather channels. In fact many FT-817, and now FT-818, owners have the same complaint. Mine also has the MARS/CAP mod. In a real SHTF situation that will be handy.

Some people buy junk radios on the cheap just to use as part donors. Glad to have been of help.

Trust me, I’m an engineer too, doing R and D new product design, and sometimes stupid crap gets done because of a mandate by marketing and upper management. They want special tweaks that lock in customers where they have to buy parts and service from us. Not everything is for well reasoned design decisions.

Ok. Some people like to use their portables as a low power mobile.

That would be a big improvement. Just about, if not all of the commercial radios where I looked at the schematics, use some type of tracking filter on the front end as well. If somebody has access to the service manual for this radio it shouldn’t be hard to tell if the same was done there. From some comments made on another site I believe the Anytone D878UV, and likely the D578UV, have tracking filters on the receiver’s front end. Very likely the reason why they cost more and perform better that your typical $20 CCR. In any case a super heterodyne design will help with image rejection if the IF frequencies are picked right.

I would wait until someone else buys one and uses it in a typical urban environment. I suspect due to the small size this is likely just another inexpensive radio-on-a-chip design with a fancy screen and more power output compared to an HT. Where these radios really fail is in the receiver section. For example I got a TYT-8600 new for $100 a couple years ago. On UHF the receiver selectively is poor. I get very strong signals showing up on various FRS/GMRS channels I know for a fact is not there, confirmed by simultaneously monitoring with a good commercial radio. In my case it was a high power police dispatch system 10 miles out and a DMR repeater at a hospital about the same distance the other direction. Remember if you can’t hear the other station because of a poor receiver then your transmit power makes no difference.

You can find these on line at places like Amazon, eBay etc. I think I got my second one off an eBay seller.

I would suggest trying this one out. https://www.dxengineering.com/parts/pry-al-800 I’ve used these on a short run of RG-58 coax. They work fine without a ground plane. The match on the Ham bands is pretty decent. On MURS and FRS/GMRS it’s up a bit but I think it was still under a 2:1 match making it usable.

https://www.manualslib.com/manual/779398/Kenwood-Tk-880.html https://all-guidesbox.com/download/499649/kenwood-tk-880-series-service-manual-70.html

Does anybody use one with an external antenna? It seems Motorola took a good radio and sort of mucked it up by using that funky stud type antenna connector. Looking at some videos, showing a stud to BNC adapter, a thin copper foil ground strap is required to be run from the inside edge of the antenna well, over the top rear edge of the radio down to the mounting screw for the belt clip. That screw is in the aluminum chassis providing the ground connection for the adapter. When the adapter is screwed in the “shell” makes contact with the copper foil ground strap completing the coax shield connection to the ground side of the radio. This doesn’t require any permanent modifications to the radio or interferes with the normal use of the rubber duck antenna. I really don’t like this since the length of copper foil from the antenna well to the grounding screw likely results in a significant impedance bump. However without it the coax just turns in to one long grossly mistuned antenna. At least with the older XPR6550’s I’m going to experiment with they use fairly standard SMA antenna sockets on the radios. I have a bunch of SMA male and SMA female to BNC adapters I can use.

If I got one for free I’m not complaining. Maybe some future update might eliminate that restriction. Likely the two that I would use are DMR and P25. The radios are very expensive and the software requires registration with license files etc. For a business they can deal with it. For a private individual for hobby use, not going to happen, not me anyway. I have a used XPR6550 VHF radio I just purchased for $75 off my favorite auction site coming. I have a used XPR6580 for $45 that should be shipping in a day or two. There is reportedly a way to put it on the Ham 33cm band. That’s why I was interested Unfortunately it seems I need the conventional version of the firmware. The radio looks like it has the trunking firmware which I’m lead to believe won’t work with the code plug hack to put the radio on 33cm. Until I can scam up the right firmware the radio will go into a storage box. I would also like to get my hands on the current version of the XPR6550 firmware for the VHF/UHF radios. Now that I seem to have a functioning version of the Motorola Mototrbo software I going to experiment with a few of them.

We can kiss and makeup. No harm done.

Yeah, I understand that. If somebody gifted me a nice Kenwood NX-5200, 5300 with all three digital modes, NXDN - DMR - P25, enabled I wouldn’t turn that down either. https://comms.kenwood.com/common/pdf/download/NX-5000_portable_Specsheet_K_02_prnt.pdf

About radios, you get what you can afford and fits your operating requirements. I don’t care if someone is using a $20 CCR or a $5,000 Motorola. I use primarily Kenwood radios, I do have a small number of Chinese ones, not because they are better, it’s just a personal choice.

Noted.

I don't make the rules. I just offered an explanation. One is always free to contact the FCC and petition for a rule change. It's been done many times before. https://www.law.cornell.edu/cfr/text/47/1.401 https://www.fcc.gov/about-fcc/rulemaking-process

I've looked briefly at those. I might consider getting one or two if I can find a super good deal just to experiment with them. I don't have any 900 MHz radios. I looked at the Kenwood TK-481's but the radio's internal IF filters kill the signal once you drop below the upper band limit. To make them really functional they need to be replaced. Second, you need a utility to put in the real frequencies since the FCC requires the use of channel numbers I believe. Not convenient for Ham use. https://www.qsl.net/kb9mwr/projects/900mhz/plan.html I noticed there is a code plug hack to modify the XPR6550 800 MHz radios. I think I can find those fairly cheap.

Oh, it's the 400 to 470 MHz band split model. Perfect for Ham Radio's 70cm band and also covers the FRS/GMRS channels too when running analog FM.

If you shop carefully you can find some good deals. I got this one eBay for $110 on an auction I won, it's a TK-5320. https://comms.kenwood.com/common/pdf/download/TK-5220_5320_Specsheet.pdf The radio looked like new, didn't have a scratch on it anywhere, not even a finger print on the display cover. I had to get a power brick to go with the charger base and the radio came with a used 3300mAh Li-Ion battery pack.