Lscott

That's possible. I did read where it's done by some radio shops to lock out the customer, in some case from the radios they own, to force them to come back for updates and changes to the code plug. That's just plain BS. I think in other cases the radio shop may have a trunked radio system they own and operate which they sell access to their customers as an extra cost service. They charge by the number of radios on the system. By password locking the radio they can reduce, or prevent, the customer from adding more radios to the system they are not paying for because they can't get into an existing radio to read it for the necessary info. That I can sort of understand.

For the moment I’m going to play around with the XPR6550’s. I need to get use to how the software works. I watched a video on how a guy recovered a password locked Motorola radio without the password or any kind of software/hardware hack required. Good info in case I ever have to do it. With Kenwood radios you’re sort of screwed without the Dealer/Engineering level CPS installed or a cracked version of the customer version. I had to do the later for a password locked used Kenwood NX-340U.

I saw that on one of the packs, no info. That's why I was curious about what was going on. You explained that well. Thanks.

Yes, I'm not surprised. That has to do with what is called "Path Loss", which is not exactly what you would think it means. When you TX the voltage component for the RF signal is independent of the frequency and is only a function of the power level. You see it expressed as volts/meter, the "E" component or field strength. However our radio's receiver also responds to that same component, but it has to come from the antenna. Since we must use resonate antennas the UHF one is about 1/3 the length, on 70cm, compared to the 2m band. With the UHF antenna being 1/3 the length the voltage induced is only 1/3 too. Power is the square of the voltage so the power is about 1/9! So if all other things being equal a UHF radio would need to generate 9 time the power of a VHF radio for the same signal strength. Looking at a typical 5 watt VHF HT you would need about 45 watts out of the UHF radio.

I already have a charger and some battery packs. Just got my programming cable yesterday from "blueMax49ers". One question about the battery packs. Is there some chip in them that stores info about the pack? One radio showed something about service life and the date the pack was first put into service. Never seen anything like this on any Kenwood radio I have.

Oh, yeah I've noticed that just about any commercial VHF HT sells for a lot more. I managed to snag a TK-2170 for a good deal, about $15. The guy whol sold it said the radio turns on, the beeps when you press the PTT button, shuts down then turns back on. He though the radio was screwed. That what they do with a nearly dead battery pack. When I got it, yup, that's what the problem was. Worked perfectly with a freshly charged pack and reprogrammed. I think the reasons why the VHF radios cost more than the UHF models, one there aren't that may out there because most business use UHF anyway. Second is the typical band split, 136 to 174, which is perfect for the popular Ham 2m band, MURS, VHF marine and NOAA frequencies.

The VHF one I have coming was only $75. The seller shows about $100 each but took my offer for less. This is the eBay item number if you want to look it up. Looks like he's sold out too. 324758091416

The hex editing was for the XPR6580. Apparently there is a code plug hack where the embedded frequency limits can be modified. The hack i specifically for putting the radio on the Ham 33cm band. I picked one up for $45. One of the parallel battery contact fingers is broken off. It still seems to work, at least it power up. Since I've never opened one of these up I have no idea how hard the connector is to replace. A few of the Kenwoods are a B___h to work on. I have a TK-3173 with a flaky volume control. I've opened up the VHF model, TK-2170 because it had a broken flex cable, it's sitting in the junk box at the moment. These radios are a pain to work on. I'm in no big hurry to work on the radio with the flaky volume control since you just about have to yank the whole guts out to get to it. I'm cheap, I guess it depends on what you want for them. They don't go for that much on eBay unless they are in like new pristine condition with chargers, battery packs etc. I have a VHF one that should arrive in the next few days.

I thought I would get a few cheap ones to experiment with and see what happens.

I typically scan the FRS and MURS channels along with several business frequencies with my radios. The Chinese radios scan rather slowly so yeah, you can miss stuff. The Kenwood TH-D74A however scans much faster. From a few tests, if I remember right, it looks like it does about 26 to 27 channels in a bit over 1 second. You don’t miss much. It’s the fastest scanning HT I own at the moment.

Welcome to the group. Don't be afraid to ask questions, that's what the forum is all about.

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.