Lscott

Don't forget about the effect from the apartment's building materials. If you have cement walls there is likely rebar in it, wood and brick may have foil backed isolation in the walls, metal tint on the windows, high lead content glass, metal blinds etc. Some newer construction has sheet metal wall studs in place of the old wood ones as another item. There is a pile of construction material that can screw with a UHF signal. The building where I work has two of the above, poured concrete walls with a loose metal mesh and the office walls have metal studs. Needless to say the reception is rather poor for weak signals for anything other than a signal a mile or so away, and trying to TX is worse.

Oh, if anybody is interested in that book I mention in a prior post you can download a PDF copy from here: https://dokumen.pub/qdownload/tapr-spread-spectrum-update-tales-from-the-rebel-alliance-9780964470750-0964470756.html

We don't have to agree, but the discussion was beneficial for those that choose to just sit back and read. If it got people to think about other points then it served it's purpose. 8-)

Frequency hopping IS a form of spread spectrum transmission. Regardless of what algorithm is used to determine the next frequency hop some communication needs to take place between the two radios so they remain synchronized. Otherwise the RX radio would need to monitor several frequencies and try to "guess" where in a fixed sequence the TX radio is currently. I did read about some radios used during Vietnam that used encryption, and I think some form of FHSS, and wasn't well received. The chief complaint was the delay in decoding the audio and for the radio's to sync up. The second(s) delay was critical under battle conditions where rapid communication was necessary. https://en.wikipedia.org/wiki/AN/PRC-77_Portable_Transceiver Types of spread spectrum modulation. https://en.wikipedia.org/wiki/Spread_spectrum

Since I don't really need the radios for critical communications I can afford to wait for a good deal. That's part of the fun collecting them, finding a good deal. The second part is trying to discover where the radio came from originally. I managed to find this out on just a few. The best one came from "Nine Mile Point Nuclear Station" out east. I think another poster knew about it and commented they replaced all their analog radios with digital. Nice confirmation of what I figured out from the names in the memory tag fields and frequencies programmed in to the radio.

It's different because it happens under automatic control and is an intrinsic feature of the transmitter's frequency and modulation circuits, and not subject to operator control on a per frequency hop, nor even what the hop pattern that's implement, fixed or pseudorandom.

That's some useful advice about simplex. That's what I was looking for. I have the Kenwood UHF TK-5320 radio, 400 to 470 band split, and use KPG-112D to program it. I would like to find the VHF TK-5220 if I can find a good deal on one in good condition. https://comms.kenwood.com/common/pdf/download/TK-5220_5320_Specsheet.pdf I do have a used NX-340(U), no display HT, I purchased and a used NX-820HG mobile I was gifted by a buddy that has no use for digital comm's. Both are the 400 to 470 band split I believe. I also have the software to program them. https://pdfs.kenwoodproducts.com/54/NX-240V&340UBrochure.pdf https://comms.kenwood.com/common/pdf/download/10_NX-720HG&820HGBrochure.pdf I would like to get an HT with a display. The older NX-200/300 look nice. The newer NX-205G/305G look good too but I only have the HPG-111D V4.7 which doesn't show the 205G/305G types as models it can program. I'm trying to get my hands on V5.21 of the software, which I hope does do the newer models. So far no luck with the zero cost option. Until I can get the software that handles them I'm not going to purchase any of the newer models. I also picked up a new in the box UHF amp, BTECH U25D, at a swap for a good price, about half of new, that should work with analog and digital modes. Good to boost an HT running mobile or as a base. https://baofengtech.com/product/amp-u25d/ https://www.miklor.com/COM/Review_DMR-Amps.php

The permitted emission types for GMRS are listed here: https://www.law.cornell.edu/cfr/text/47/95.1771 The FCC emission designations are listed here: https://www.electronics-notes.com/articles/radio/modulation/itu-radio-emission-designators.php And yes the FCC does in fact use the ITU emission designations as do many countries. Note under "Character 5 details of multiplexing" letter indicator "C". This does not appear in any of the permitted emission designations for GMRS. Depending on which source you consult FHSS, frequency hopping spread spectrum, could also be designated as an "X" in the emission type, a type not covered by any of the other types. This also does not appear in the permitted emission designations for GMRS either. Then the very name "spread spectrum" of course implies the signal is spread out over a range of frequencies. The permitted bandwidths on GMRS are only 20Khz and 12.5KHz. Having a signal hopping around many times per second would be effectively a wide band signal exceeding the permitted bandwidth. Again, IMHO, I think this would exclude the use of FHSS on GMRS. If somebody has a different opinion that's what the form is here for, a friendly discussion and debate.

It wasn’t clear so I was questioning it. I would have to go and double check on this point but even on the Ham bands the FCC specified the spreading code was allowed at one time. That might have changed over the years. https://www.law.cornell.edu/cfr/text/47/97.311 https://files.tapr.org/tech_docs/Ham_Ethernet_GBPPR.pdf I have a book on my shelf written by TAPR, Tucson Amateur Packet Radio Corporation, with the title of “Spread Spectrum Update - tales from the rebel alliance”. The book covers spread spectrum technologies and some of the basic math behind it. This also includes issues with interference etc. The book was published in 1998 so a few things have likely changed since then. It’s primarily aimed towards Ham radio of course.

Sooner or later I should add a cheap Fusion digital radio to my collection. The GM club operates a wide area coverage repeater from the top of the now called GM headquarters building in downtown Detroit. Most people still call it the RenCen. http://www.gmarc.org/wp/wp-content/uploads/2020/05/RenCen-repeater-qsl-compressed.jpg

I just got a 7% off offer on a NX-200. Not biting on this. The seller has a huge number of radios being sold in other ads, different models. Sooner or later he’ll get tired of the inventory not moving. Out of 25 units of the above radio he’s only sold 2 in the past week. I’ll wait for a better deal. He won’t lower the price on single units per a response to a “best offer” option in his ad. Oh well he can keep them. I just buy radios as a hobby to add to my growing collection, I really don’t have a burning urgent need for them. I can afford to pass up ads if I don’t like the price or the seller doesn’t want to deal.

The questions I have are first is this even legal on GMRS? Second with the small number of channels available just how effective would it even be? I don't think you would want to be doing this on the repeater input channels. The low power FRS ones are sort of useless which leaves just channels 1 to 7 to use. The frequency hopping radios I've heard about are digital, and digital voice is not allowed on GMRS anyway.

Yeah, simplex around here is sort of dead too. I very infrequently hear any CQ calls on 146.52, even when mobile, my primary operations. I try to respond to the 52 calls when mobile due to the low activity I observe. I have radios for D-Star, DMR, P25 and NXDN so far. I'm was wondering what to use for simplex operations. Seems like just about everyone uses repeaters since they are typically linked. I wanted to include some simplex channels in the various radios I have to supplement the repeater channels. That leads back to the thread's topic, pros and cons. Talk groups and networks. I know on DMR that TG-99 is the talk group used for simplex operation, but what about the other modes? This gets into the area where I've found separate networks, even for the same digital modes, where the talk groups are not entirely the same, however there has been progress in that area. Then there are the bridging issues. This all seems to be a very unnecessary complication. Here are some examples. https://brandmeister.network/ https://dmr-marc.net/ https://w8cmn.net/mi5-sites-talkgroups/ http://www.nxdninfo.com/ https://w8cmn.net/p25/ Then the last point is usually you get just one digital mode per radio model or manufacture. I did hear about a couple of people that hacked the MD380 hardware where there is the possibility of getting a multi-mode digital radio without the astronomical cost from manufactures like Kenwood and their NX-5000 series multi mode radios along with the licensing crap that goes with it. I read somewhere the programming software for them is a POS. That's another problem area. Some manufactures CPS, customer programming software, is rather easy to use and or well organized with a good help system. One of the very popular Chinese DMR radios their CPS sucks. It's buggy and the built in help is almost worthless since there is basically "maybe" a line or two describing a feature. The other choice is looking at a bunch of YouTube videos hoping the area one has an interest in gets covered. Other's like Kenwood keep their training materials locked up behind a "dealer" login portal. I suppose that's done to support their dealer network, they want to discourage customers from programming their own radios. and funnel business to the dealers. A personal observation it seems most digital voice modes are mostly used on UHF. I'm assuming it's because you can find good commercial gear for UHF far easier, and cheaper, that on VHF. Second there is just simply more spectrum where people can spread out. I've been looking for some select Kenwood VHF analog/digital radios for a while. The few I see on the major auction site usually are much more expensive than the UHF model, if you can find one at all. I'm looking at an NX-200-K2 at the moment if I can win the auction without paying a fortune for the radio to add to my "collection." Around the Detroit area, where I'm at, there is little P25 activity and there is only one NXDN repeater listed for the whole state, and I don't think it's even linked into a network either.

I know some operators get very annoyed when monitoring their favorite FM simplex frequencies when a digital station pops on on one. That's lead to digital voice operators to use "suggested" frequencies reserved just for digital voice modes. What are the typical frequencies used for digital voice modes when using simplex? I found several recommendations for 2m and 70cm. It seems like there are only a few suggested frequencies. Since there are several digital voice modes used, (D-Star)(DMR)(Fusion)(P25)(NXDN) and some others, are separate simplex channels used for each or all lumped together?

Yup, it takes a lot of work and time. I had to apply some significance pressure to make progress. It's slow but does work. When you get to the point where you're happy with the result lighten up on the pressure, and as you observed, do circles to buff out any remaining swirl marks. I've also experimented with using an electric toothbrush as well with some modest results. I put a small dab on a paper towel and went to work. I use the toothpaste just as it comes out of the tube. After polishing for 5 to 10 minutes wipe off the toothpaste then tilt the screen to get a light to reflect off the surface while looking at it. This highlights any scratches in the plastic so you can see how much progress you're making. One hint. Use tape around the edges of the screen. This keeps the toothpaste from getting into any buttons and keys nearby. Don't ask me how I know this.

Myself I'm leaning towards DMR. Fairly cheap hardware is available. You can get reasonably priced Chinese radios. Then move up in performance to the commercial vendors, Icom, Kenwood and Motorola, yeah they cost more but have less issues than the Chinese ones. I have a collection of radios for D-Star, DMR, P25 and NXDN. Nothing for Fusion yet. If one is interested in P25 or NXDN your only real choice is getting a commercial grade radio. As far as I know there are no "amateur" level radios being sold for those two. Around the Detroit area, where I'm at, there is very little P25 and NXDN activity. In fact there is exactly ONE repeater in the whole state that is listed in "Repeaterbook.com" as being NXDN enabled! I don't think it's even networked. https://www.repeaterbook.com/repeaters/feature_search.php?state_id=26&type=NXDN Around the west coast area of Florida NXDN seems to have a fair bit of activity. https://www.repeaterbook.com/repeaters/feature_search.php?state_id=12&type=NXDN There are a few P25 repeaters around. https://www.repeaterbook.com/repeaters/feature_search.php?state_id=26&type=P25 Most of the digital voice modes seem to be mostly used on UHF. That's fortunate since its far easier to find used commercial radios that do analog/digital in the UHF versions. The VHF models are not so common. And, in my case, the VHF Kenwoods seem to be expensive relative to their UHF versions of the same radio model, particularly for hand-held radios. At lest all of the digital radios I own can also do analog FM too. Not everyone has a digital radio you're going to talk too. The CON to the whole digital voice mode is if you want to use a different mode you're likely stuck buying another radio. Yes there are some out there that do more than one digital mode, and have a huge price tag, but none do all of the modes. You want to talk D-Star hang a radio for it on your belt, want to do DMR get another radio and hang it next to the other one etc. Petty soon your waist line is going to look like a Batman's utility belt full of HT's.

Yeah, one of the radios I have has the flaky PTT button. I seemed to have fixed it by being a bit aggressive by repeatedly hitting it strongly a few dozen times. Now it seems to be working OK. I suspect the internal contacts get a bit dirty. Getting the contacts to close with a fair bit of pressure for a number of cycles should clean the contacts up a bit. If they get corroded or oxidized there isn't much that can be done.

One thing about the hardware for the 6550's and the 6580's. The volume controls don't seem to have a solid "click" for the off position. I can just barely hear it and feel it on several of the radios I have except for a couple which has a good feel to it and makes a distinct click. I'm guessing this is a common issue on these after a period of use? The radios turn on and off OK, volume seems to function fine, just have to watch the display to be sure. I'm guessing it's the case since I've seen batches of volume control pots for these radios for sale on eBay because they need to get replace frequently.

Is it you just get a communication error or some other message? A few unlucky people get stuck with a used radio that is password locked. One thing to check if it's a communication issue is the quality of the programming cable and the port on the radio it plugs into. Sometimes the cable port contacts are dirty or the cable isn't fully inserted into the socket. On the issue with programming cables, the USB to serial type you commonly see people use, could have a counterfeit Prolific chip. The official Prolific chip drivers can detect those and simply refuse to work. A lot of people have gotten burned on cheap cables due to the counterfeit Prolific chips used in them. The best cables use the FTDI chip.

I see the point. Thanks for the reminder. Ended up typing first and thinking later, not a good combination.

I should add the recovery procedure completely wipes the radio leaving it with the factory empty code plug. There is no chance the old code plug can be read out of the radio when the procedure is completed, it isn't there any more.

All the procedure allows is to reprogram the radio. The feature is built into the CPS, it’s not a secret, and it is clearly called “recover”. What it doesn’t do is allow one to read the existing code plug out of the radio. That’s an important point if one gets a radio programed for a trunking system. You don’t want rogue radios on the system. If one had the code plug they would have the info necessary to program other radios. The password function is not there to prevent theft of the radio or it’s use. If you wanted to prevent a stolen radio from being used “on the programed frequencies or trunked system” that’s why there is the “stun” feature.

Yup, Kenwood has the tuner feature in many of their CPS packages. I'll agree you can really mess up a radio if you're not careful. I got the package because it was used by another guy when he was breaking the password protection on the Moto radios. You save the current tuner values in the radio to a disk file, then "recover" the radio by loading the firmware and code plug through the Mototrbo CPS. Then to be sure you reload the radio's tuner values. You should then be able to read an empty code plug out of the radio without getting the password prompt anymore.

Yup. in the case of the TK-5320 the other guy had a much higher bid limit set. I'm sure he thought he was going to get a really good deal. I could see where it appeared he made more that one bid, but the amount displayed didn't change. I figured he had adjusted his max bid up a bit. I also look at the number of items a bidder has purchased. When you see 100's to 1000 plus purchases you know the bidder is likely looking for that cheap deal where all they want is to flip it later for more money. You very rarely see them bidding up an item. It's the low purchase number bidders you have to watch out for, those are the people that run the bid amounts way up. Buying stuff on eBay has a lot to do with the psychology of the other bidders, and sometimes the sellers. A few times I've sent a message to a seller asking if they will take about 2/3 of their "buy it now" price even it they don't offer a "best offer" option. You would be surprised how many sellers consider it and a number took my offer! Squeezing every last cent out of a buyer isn't their goal.They just wanted to sell the item and be done with it. If you don't ask you won't know.

Sure, you can set a max bid then walk away. However the bidding never really seems to start until just minutes before the auction closes. A few times I was the only bidder. Still can't figure out why that happened. There was nothing wrong with the radio. I guess at the time nobody wanted it.