gman1971

Shame the Motorolian empire doesn't have an HF mothership in their radio fleet... oh well... ugh... TYT... oh man, I am trying to sell them all... but nobody really wants them... I think you'll be very pleased with anything XPR... and I have a couple of XPR6550 UHF for sale, if you're interested. G.

Very nice. GM300, are those hard to program, what do you use? I am mostly into XPR and EVX radios... most of the older stuff I haven't messed with it much... if at all. G.

My fellow Motorolian Citizen... and no Baocrap on this picture... ah perfection... G.

Well, I am asking how did you measure desense? To do so you need to perform an ISO-tee, otherwise you're just guessing what the real problem(s) are. A car AM receiver is not meant to pick weak SETI signals from outer space... its meant to pick kW broadcast signals nearby, so it doesn't need to be that good. Again, you need to invest in measuring equipment if you want range without requiring the use of other people's infrastructure, which I did, and very glad I did. Now I can determine what the problem(s) are by performing measurements in troublesome spots. Once you know if its desense, or intermod, or PIM, a bad antenna, crap cable... etc... then you can find a solution. Until then its all a guess, and guesswork gets really expensive, really fast.... Selectivity means filters, preselectors, cavities, etc... all those increase selectivity of a superhet. Which translates into "you probably need to invest on preselectors and cavities" but again, without performing any measurements, its only a guess, but one thing I've learned is that more selectivity never hurts... you just have to determine when too much selectivity is too much, and for that you need to measure. Marc, a member from this forum, was the person who first introduced me to the concept of filtering a long while back... that is when the range started to increase... G.

http://www.ittc.ku.edu/~jstiles/622/handouts/The%20Preselector%20Filter.pdf

No R70?? how come? are the GM300 good?? They must be... nice nice!! G.

I cannot without being there to asses and perform an ISO-tee. What I can tell you, tho, is that if those two RF firebreathing angry towers you mention in your post are nearby where you live, the desense (if any) will be the same up to about 10-20 miles away, maybe even more. The Candelabra tower <2 miles from base here has multiple kW broadcasts, range is 100+ miles... that is a lot of dBm coming out of those towers. With that said, since you were at the bottom, or near the bottom of these towers, you'll get the highest null since most of the radiated energy is projected towards the horizon, not downwards; hence why repeaters use vertical separation when using a TX and RX antenna pairs. Desense is only part of the problem, then there is intermodulation. Most CCRs which claim to have superhets have no tuned front ends ($$$$). B/c how a superhet works is by converting signals into IF frequencies, when the incoming RF that gets through into the IF stages is a multiple of the IF stage frequency, then it gets mixed with the desired signal (intermodulation), and while the receiver might've not desensed significantly, you still get a garbled signal, or nothing at all. During tests performed on EVX-5300 mobile setups I realized that the measured signal strength was about the same with and without a RFS preselector (whcih adds a 1.5 dB insertion loss), but without the preselector the EVX-5300 mobiles were getting a garbled, almost unintelligible audio in NFM, even though the signal was there and about the same RSSI. Adding a preselector increased effective sensitivity by just 2 dBm, which isn't much, but the signal was now crystal clear as opposed to before which was all garbled, even with the 1.5 dB Insertion Loss from the preselector. Again, superhets work by using intermediate frequencies to reject unwanted stuff, problem is that without a tuned front end it won't reject the incoming frequencies that are multiples of the IF stage frequencies. IIRC the EVX-5300 has a 5 varactor tuned front end, and the superhet was getting hammered by RF towers in the Madison WI area... it needed me adding a -60dB preselector filter to properly receive signals that otherwise couldn't before, not due to sensitivity, but due to selectivity. A radio without a tuned front end is going to require a lot more than just a simple preselector to work... which explains why the 5550e demolishes every other radio I own in range tests... b/c its selectivity is off the charts compared to anything else I own, along with its effective sensitivity. My findings can be summarized in one sentence: Range increased when selectivity improved. The more selectivity the radio being tested had, the more range I had, as measured... which seems to match my astrophotography parallel experience, the narrower the band of the filters I used, the better I could pick up stuff like the horsehead nebula, etc, in heavily light polluted skies. Selectivity == $$$$ G.

Nice!! Motorolian motherships... G.

replied.

Well, if someone has taken the time to pay for their GMRS license, and taken the time to post here, asking questions, then it would seem logical to me they might want to know the difference. Ignorance makes anybody an easy target for misleading claims, misleading advertising and anything in between, and more. I don't know how many broadcast towers/stations are in the location where the OP lives, but I am certain the answer is > 0, and all it takes is a one of those RF firebreathing angry 1000 foot towers to screw up the front end (or lack thereof) on nearly all CCRs... How do I know? B/c I've owned several CCR mobiles that couldn't hear their own way out of a paper bag... no matter what. It wasn't until I started purchasing 2nd hand Vertex Standard LMR gear that I realized that those CCR radios needed several hundreds dollars worth of preselector/cavities to make them come even close to what a lowly Vertex Standard EVX-5300 mobile could do with nothing but the radio mated to the antenna... While I think CCRs walkies have their use, going CCR on a mobile is, IMO, a waste of money. Why? b/c If you don't see a range in the 10+ mile range, with a couple of 25W mobiles, one at base, and another with an NMO 1/4 wave antenna on a car then chances are the receivers are garbage. Been there, done that. Again, you can all gang up on me, saying how horrible, cocky, hurtful, etc etc, gMan1971 Motosnob comments are, how he is not very PC, how he is hurting my feelings about my expensive CCR mobile, etc, etc... In the end, all my business/personal family radio range problems ended once I started listening, and doing things the same way professionals build their commercial/LEO grade communication networks, and that meant using the same equipment they use, and saying bye bye to ALL CCRs... and surprise surprise, my radio range started to increase, and is now measured in tens of miles, rather than tenths of a mile. If transmitting with 25W doesn't reach, 50W is not going to make the slightest difference. A 3dB increase is nothing when rolling terrain can attenuate the signal by -10 to -20 dB... then you add that -20dBm attenuation due to receiver desense, and you have a -40dBm signal drop, which means, you hear zip. The TX guy cranks power to 50W thinking it has to reach now... but all you're doing is reducing the -40 dBm attenuation to a -37dBm.. still 37 dB short of hearing zip. G.

Everything was going well until I read the words Retevis.... anything made by Retevis doesn't belong in the same sentence with Motorola. DTR radios are a far better radio than anything made by Retevis will ever be. At that point you might as well use a XPR4550 in FM UHF (GMRS) and a DTR7xx with a simple repeater controller. The DTR radios will get you the indoor performance, the XPR4550 mobile will give you the punch to get far, with an excellent receiver with a proper front end so it doesn't desense when the neighbor turns his LED exterior lighting. G.

That is correct, mbrun... thank you. Not giving up on GMRS.... why would I? I am selling a lot of my radios b/c I want to consolidate, so all the XPR7550e and SL7550 radios that I've recently acquired... those stay, aka the new Motorolian Imperial Fleet. Also, a lot of the radios I am selling aren't really the lowest of the barrel I own either. For example, the EVX-539 is not a CCR by any stretch of the imagination, but the XPR7550e won the contest, for several reasons other than just better performance. For example, I can't deal with having 10 different codeplugs anymore, nor 10 different CPS, 10 different battery chargers, 10 different prog cables... etc. So everything non Motorola XPR gen2 will have to go at some point or another. I debated whether to keep the XPR6550s Gen1 radios, but I figured I might just sell them as well... maybe these can help others see the light the way they helped me see the light... Oh, and there is also two more Alinco MD5 DMR/FM radios up for grabs as well. I just forgot to put them on the "yard sale" post... G.

EVX radios are not really made by Motorola, even though Vertex owns Motorola. The EVX line were the last true Vertex (designed in Japan) radios before Vertex became fully absorbed into Motorola. CPS, firmware, etc, is all free, it was free even when in service. Cable can be found for cheap on eBay as well. I understand about the kenwood cable, and CCRs, I have all kinds of CCRs, so I used to know the pain of having to deal with different chargers, batteries, CPS, cables... etc... G.

I think based on receiver specs the Vertex Standard EVX-531 could be a better radio, IMO... which also supports DCDM and most advanced DMR features as well. G.

Up for your consideration... Pictures upon request... Prices are all negotiable, you can PM me for programming for the Motorola/Vertex radios. Please, ask if you don't see something listed on the descriptions. If you feel something should've been included, or its missing then PM me, please. Also, radios are listed locally and other internet sites as well, but I'll try my best to keep this list updated. Two options: ->Local pickup, cash only. I live in the Madison, WI area. ->Shipping to CONUS only, PayPal gift. Inventory for sale. x1 - Motorola XPR6550 portable, VHF only (136-174)(GPS) Excellent condition. Battery, antenna and M charger. $195 local pickup. $205 shipped. x1 - Motorola XPR6550 portable, VHF only (136-174)(GPS) Excellent condition. Battery, antenna and VS charger. $185 local pickup. $195 shipped. x1 - Motorola XPR6550 portable, VHF only (136-174)(GPS) Excellent condition. Battery, antenna and VS charger. $185 local pickup. $195 shipped. x1 - Anytone AT-578U/V mobile, tri-band: 140-220-440, DMR/FM (GPS), upgraded with trimetal N connector. Excellent condition. Microphone, GPS antenna, mounting bracket. $350 local pickup, $360 shipped. AES encryption capable. x1 - TYT UV-8000E portable, UV, FM w/crossband repeat. Excellent condition. Same as new items included. Box, charger, cable, antenna, etc. $50 local pickup, $55 shipped x1 - Alinco DJ-MD5TGP portable, UV, DMR/FM (GPS), Excellent condition. Comes with everything as new. PLUS a shoulder microphone. $140 local. pickup, $150 shipped. x1 - Alinco DJ-MD5TGP portable, UV, DMR/FM (GPS), Excellent condition. Comes everything as new PLUS a spare battery and a shoulder microphone. $170 local. pickup, $180 shipped. SOLD x1 - Vertex Standard EVX-531 portable, V only, DMR/FM no display. Excellent condition. $80 local pickup, $85 shipped. AES encryption capable SOLD x1 - Kenwood TH-F6a portable. all band all mode w/SSB receive, 144-220-440 transmit. Mars-cap enabled, in Good condition, missing the PTT paddle and the microphone rubber cover, clean screen. Comes w/antenna and battery. $150 local pickup, $160 shipped. SOLD x2 - Radioditty GD77 portable, UV, DMR/FM. $80 local pickup, $85 shipped. Excellent condition. Chargers, UHF Vertex Standard antenna, 1 programming cable. SOLD x1 - Motorola XPR6550 portable, UHF only (400-470)(GPS) Excellent condition. Battery and antenna only. $130 local pickup. $140 shipped. SOLD x1 - Motorola XPR6550 portable, UHF only (450-512)(GPS) Excellent condition. Battery and antenna only. $130 local pickup. $140 shipped. G.

Wonder if the FCC is even legal on that, especially after the whole Rugged Radio FCC letter... most of those radios were supposed to be "Scanners" under FCC... with a PTT? G.

Well, it doesn't need to be a sharkfin, any regular antenna that is mounted in the roof would work, you just replace the entire base, put the NMO and relocate the GPS/XM/AM/FM circuitry on the tail light. G.

Much better way to put it than the typical gMan1971 this radio sucks... Your last statement is pretty much defines what makes a radio work well. Superhets alone suffer from out of band interference, mainly due to intermodulation caused with the IF stages frequencies... at least without the presence of a decent front end. So, don't let the superhet buzzword get you... G.

Another option I've found to be a good compromise is to remove the sharkfin/oem antenna on the roof and install the NMO mount there. I've relocated the sharkfin internal components to the spoiler or to the third tail light on my cars. Saves the hole drilling dilemma, its easily reversible and no more scratching paint magmount shenanigans, or any other magmount issues. Works sufficiently well, although its a little less optimal than drilling the hole in the dead center of the roof... but my cars/vans have large panoramic sunroofs so makes it quite impossible to drill holes on a glass roof... so, the only place left is the OEM sharkfin location. UHF is not as bad as VHF, a 6 inch antenna is not even noticeable on a minivan. G.

I know I stated I'll give it up on the CCR crusade, but this, what mbrun stated, is also part of the reason why I am so "outspoken" about those radios in general... G.

From the grumpo-gMan1971, the Motosnob... Anyhow... happy Thanksgiving to all... God Bless and GodSpeed!! g.

About darn time. I didn't believe what I read on another site, but these radios seem to be branded as portable scanners too... who knew. G.

+1 to mbrun. Also, remember that radio is a SNR game, or a Signal to Noise Ratio game.... sometimes the Signal might still be there, faint, but masked by the overwhelming Noise... much like light pollution under the night skies hides the fainter nebulae, stars, etc... you throw an H-Alpha filter, and all of the sudden the faint wonders of the night appear much clearer... same with radio. A few feet higher might not make the range noticeable better, but it seems to make the current link quality a bit better... and sometimes every bit counts. Also, remember that not all antennas radiate perfectly towards the horizon, there are nulls on the radiation pattern, both vertical and horizontal... and problems with grounding, problems with feedline, etc... they all introduce nulls on the pattern. So if a subscriber is in one of the antenna nulls will have the same effect as being behind difficult terrain. Wish I lived in a place with no obstructions... with no angry RF firebreathing broadcast 1400 foot towers... G.

And there could very well be not be a shred of difference... however, I've learned (the hard way) that extra adapters, that might be seemingly innocuous (as measured), can sometimes severely cripple the entire system, due to impedance mismatch, being lose, introducing PIM due to dirty threads... etc. Loss is only a small part of the picture. I currently have a 3dBm IL on my entire feedline chain, it hasn't negatively affected the slightest bit in the range I get. In fact, I get a lot more range now with a 3dBm loss in the feedline than I ever did before with just a single LMR400 cable terminated on PL259 connectors going from radio to antenna. G.

Fair enough. I'll give it up. I've edited my posts accordingly. And sorry for the trouble, I was only trying to save people some money in the long run. G.