gman1971
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Posts posted by gman1971
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Hey guys, I just ordered this radio replace a lost radio.
Don't have it yet but I've been doing a lot of reading and research over the past few months (radio is been delayed time after time) and it looks like it has a fairly decent hybrid receiver, the 1st stage seems to be a superhet and the 2nd stage is a direct conversion. According to ppl who've tested it it has pretty good selectivity and fairly decent sensitivity, along with a myriad of options, including two receivers, crossband repeat (all modes, DMR/FM or FM/FM or DMR/DMR), single frequency repeater for DMR, bluetooth, etc....
Does anybody have any thoughts? have you guys tried this radio?
G.
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If you want to do an "in-band" repeater you will need two radios, a duplexer and a controller as the main components.
You can buy a cheap UHF duplexer at this site. If you supply the two frequencies they will tune the filter at no extra cost. Also don't forget to get any N to whatever RF adapter you will need to connect to the radios and the antenna.
www.409shop.com/409shop_shopcat.php?&usercat=4942
If you want to know how well these cheap Chinese duplexers work a guy did some testing on one here.
http://www.repeater-builder.com/antenna/pdf/chinese-mobile-duplexer-measurements.pdf
Then use a simple repeater controller like this one.
https://radio-tone.com/product/rt-crc1-repater-controller-full-duplex/
I see ad's for the "Surecom" controllers but have read a lot of bad or poor reviews. The one above seems to be OK. Also don't forget to get the right radio interface cables with it.
I've had good luck with surecom controllers, but then again I only have 2, so the sampling is very small, perhaps I got just 2 which were good? Mine are battery operated too, so I can use them on the go. They are the only ones I've tried that will work on Anytone radios, all others I've tried will cut the first 1/2 second or so of the transmission.
G.
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Nice find!! Balloon would work too....
Altitude is certainly king when it comes to higher freqs like VHF...
never thought about the drone but wanted to try this some day just for fun (Balloon Experiments with Amateur Radio) http://bear.sbszoo.com/
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Yeah, I've heard them too, but in the past, nowadays MURS is pretty dead around where I live. I've done some data telemetry with packet radio, fun stuff... 2W with a good antenna will reach ridiculously far if placed at the right location... my record was 30 miles, but one of the radios was strapped to a drone... so I guess that doesn't count...
G.
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That too. Parrot has the advantage of only needing 1 radio.
G.
Or do a "parrot" repeater. This is where you TX and the controller will record the message. When you're done it then re-transmits the message. This of course slows down the communication, and some find them annoying to use, but are simple to setup using one radio and fairly cheap. There are several YouTube videos where a guy did this putting the guts in an ammo can with a battery and charge controller connected to a used solar panel. He used the metal ammo can for the ground plane required by the antenna. Stuck it on a mountain top in a very remote area. Had it there for about a year or so running before having to service it.
The repeater controller he used should be like this one.
https://www.argentdata.com/catalog/product_info.php?products_id=98
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You could just do a simple GMRS simplex repeater with two radios (one mobile and one portable, for example). Have the portable radio RX and TX on low power on freq #1, then have another radio, a mobile, set to RX and TX on high power on freq #2. You set freq#2 to whatever GMRS channel you want to reach far away, and set freq#1 to whatever your portable is. Use a repeater controller to connect the portable to the mobile and two antennas. If you use low enough power on the freq#1 side (potentially adding a 10dB attenuator inline with the portable to antenna) you won't need any cavities and it should work rather nicely.
G.
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Also, my primary GMRS long range link is all done using Vertex Standard commercial gear. As I've quickly (and expensively) realized, sticking anything UHF non-commercial grade to the Diamond X50C2 (a 7.2 dBd UHF gain vertical antenna) immediately blanked out, desensed, the receiver due to the massive RFI coming from the 1400-foot Candelabra tower that is less than 2 miles from my house... None of those CCRs has afforded me more than ~2 miles range (except the MD5, which is an improvement, but at 189 a pop, its hardly a CCR), no matter what kind of antenna or how high it was placed, even with a couple of 100 dollar cavities... these CCRs couldn't hear squat, not even the NOAA stations, except for the one at 162.550, which is coming from the 1400-tower 2 miles from home. When you want real range, measured in tens of miles (rather than tenths of an inch), range that works reliably, its time to save up and get a real Motorola/Vertex/Kenwood/Icom radio.
Now, if your aspirations are to reach the grocery store down the street, awesome, a CCR might be enough. But when I hear guys like @marcspaz talking about how he was chatting with guys over Spain from the US over HF radio, that IS mind-blowing... grocery store? not so much, man. Maybe it was mind-blowing back when Marconi invented the radio... nowadays? the bottom of the barrel BF-888S can do it too, for 9 dollars a pop.
Then there is the Zello app, if you like two-way style comms, it uses the cellular network and its free!, better, and more reliable than any CCR would ever be.
G.
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He meant the GD77 S, the S model has no screen, and that is an overpriced CCR. The BF-1801 (with screen, a GD77 clone) has its place: its a cheap intercom radio for short range comms.
I understand, I carry an Alinco MD5, which is basically a small 878, I like having the dual band option, even though I am not a ham, I have pretty much every single ham FM repeater in Wisconsin punched in the radio, in case I ever need help, or in an emergency. Most of these no screen radios are kinda limited for anything beyond store floor intercom (which is what they are designed to do, anyways)
There is a noticeable difference in Receiver performance between tne XPR7550 and the XPR7550e. I don't carry one b/c I don't have one, yet. Aside from the price tag, you're boxed in a band, either VHF or UHF... can't do anything to convert... at least I haven't taken one apart to see what makes these radios different... if its a software (firmware) thing, or a physical hardware change.
G.
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I am glad you're happy with the GD77s, but if you really want to see mind-blowing performance then you should get yourself a pair of XPR7550e and see...
Also, if you are using the GD77s on DMR then it is not legal. GMRS is FM ONLY. Also, to be 100% compliant then you should be using 20 kHz wideband, and because I know that the GD77s won't do 20 kHz, then you should be using 12.5 kHz instead. If you're using 25 kHz then it is not legal either.
You speak like people here in the forum don't know what they are talking about, they are called CCR for a reason. Don't mislead people, dude, grocery store could be 1/2 miles away from home. That is hardly mind-blowing. One radio sitting on a 10 floor building to ground level, not really mind blowing either. I've reached 30 miles using a 2W VHF MURS Ritron portable... does that mean the performance was mind-blowing? Certainly not, why? b/c the receiving radio (a TYT8000E with crossband repeat) was strapped to a drone flying some hundred feet up in the air in the middle of nowhere.
Also, for the GD77S, at 75 dollars a pop you are being ripped off, man. If you want cheap, try the Baofeng DM-V1, which is basically a GD77s, except its 25-29 dollars a pop. The DM-V1 will also do DMR if you really want to have DMR (not legal in GMRS). Then there is the Baofeng BF-1801, 45 dollars a pop and its a GD77 clone, with a REAL screen. However, at the price you paid for those overpriced CCRs you could've bought a TYT MD380 UHF (single band, not the dual band), with a color screen and, IIRC a real superheterodyne receiver too... and have a better than mind-blowing performance over the GD77S... I think paying 77 bucks for a CCR without a screen is a ripoff, fortunately tho, it is great to know that, at least, the performance is mind-blowing. You could've achieved the same kind of mind-blowing performance with a pair of BF-888S, except for 18 dollars, and have enough cash left to purchase a used Vertex Standard EVX-531 on eBay, maybe 2 if you look hard enough.(since you seem to like no-screen DMR capable radios)
Also, I didn't make this post b/c I am brand name snob that just wants to bash on CCRs for the heck of it, so, without further delay let me introduce you to my extensive CCR collection, and the reason why I made this post.
-15 BF-888S, yep, at 9 dollars a piece, they work great for my house intercom, and if anybody destroys one, guests kids, anybody, be it by throwing it the toilet, smashing it with a hammer, etc, etc, won't be crying over it. Receiver on those is BETTER than the GD77s.
-10 Baofeng BF-1801, basically a GD77 clone. Those work great as intercoms on both DMR and FM with the signaling stuff.
-5 Baofeng DM-V1 (which is basically a GD77s, but UHF only, can be modded to do VHF, but haven't tried to do that) Great for store floor intercom, and at 25-29 bucks a pop, its hard to argue with that.
-2 GD77, I got ripped off twice before I found out that the Baofeng BF-1801 was the same radio, at HALF the price. The GD77 is a ripoff, get the BF-1801 instead.-4 Alinco DJ-MD5 DMR/GPS. Not exactly a CCR at 189 a piece, but these are usually our carry around radios, one for each member of the family (old enough to use a radio) Good balance between features and RF performance, for the price, of course.
-5 Baofeng GT-3, (3 dead now) those were the radios that got me into FRS then into GMRS.-4 TYT 8000E.
-1 Anytone INSTG8R
Forgot to state what I no longer own but that was also extensively tested.
-1 Retevis RT52, one of the worst, if not the worst radio front end I've ever benched, returned.
-3 Anytone 878UV. Too big, I liked the Alinco MD5 beter, returned them all.
-2 UV-5R. All dead.
-2 UV-82. Gave them to friends.
-2 UV-3R. All dead.
-Ailunce HD1. Very poor performance, returned.
I've tested all these radios in nearly every possible scenario you can think of, with several types of ducks, high gain antena, etc, and with the exception of the Alinco DJ-MD5/Anytone 878 (which seems to have better front-end filtering that all those CCRs) none of these radios can compete in terms of range and overall performance to my commercial grade gear, especially when operated in crowded RF areas, which is pretty much anywhere where computers operate these days. Inside a mall the difference is night and day.
G.
Believe it or not, the GD-77S is my favorite radio at the moment. It solves practical problems by slinging squiggles, and it's even type-accepted as a business radio (No FPP). As such, it qualifies as the "surplus commercial equipment" that the 2017 memorandum stated was never intended to be banished from the GMRS, and I believe it's legal under the latest regulations.
And at five watts, it's my most powerful cheap squiggle-slinger. Used with Motorola gear (2W) on both high and low (1W), it's absolutely comprehensible in two directions when cell phones aren't getting enough signal to send a text message.
Is it "good"? Apparently not. Is it good enough? For me and those like me, yeah it is. (And if it gets dropped, I didn't just break irreplaceable hardware!)
Edited to add: And at 5w back and forth, it'll reach from handie to handie all the way to our grocery store, and inside too. As far as I'm concerned, that performance is mind-blowing.
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Very nice!! I am not sure if those will play well with the vertically polarized 1/4 wave car antenna... I guess I can just build one and try
Thanks Marc!
G.
G, here is a good link you can use. It will help you understand how a horizontal quad loop works, why its omnidirectional, and why there is such good natural noise reduction in the design.
I am building this to scale for 80 meters, but you can easily build a VHF version. My friend has his fed with ladder line in the corner closest to his house and its 35 feet off the ground, due to the frequency its being used on.
You cut the ladder line to length for tuning the SWR, as the ladder line is part of the antenna design.
http://www.caarc.ca/articles/horizontal-quad-antenna -
Looks like the loop is a horizontally polarized antenna, so that probably won't work. Certainly easy to build. The folded dipole phased array might be the better alternative. Perhaps the double zepp is another one I've been eyeing, not sure about the radiation patter on those..
Also, there seems to be a way to alter radiation pattern with stacked/phased dipoles.
I live in one of the highest points of the area too, so perhaps that is why the 5/8 is working better. Things are starting to make sense.
G.
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This one has just S11 and S21, I don't think it can measure the voltage...
G.
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Always super helpful! Thanks Marc!!
So, as for the 0.XX uV scale, could I measure that using the nano VNA? I can read dB on the S21 side of the VNA... I've used that to determine noise floor measurements on the new antenna.
The EVX-5300 is rated at 0.25 uV 12 dB SINAD.
Certainly agree, the 5/8 will probably remain up for the foreseeable future. Perhaps those extra 4 feet of height I added to the mast did help...
When I took the triple 5/8 apart after bringing it down I noticed it had water inside, some of those foam inserts that keep the antenna straight up inside the radome were soaked, so perhaps that was part of the reason why performance was so weak. I won't be able to put the triple collinear 5/8 wave back up on the mast until the 10th, but it would be interesting to see if these extra 4 feet of height is what really made the difference, or if the radiation pattern is the culprit, or both...
I have considered a dipole. I've looked at those commercial folded dipoles as well, these probably seem the way to go. A loop has never crossed my mind, but it looks like I have some homework to do now! Thanks!!!
Wow, an 80 meter loop? that is going to be one heck of a giant antenna!! hahaha...
G.
Hey, G... Do you have a meter that can read 0.XX μV scale? I thought you told me you have an analyzer and the voltage was low. Is that correct? If so, what is the voltage reading going into the radio from the antenna transmission line, without the preamp?
The filters help eliminate noise if you have poor selectivity, but the preamp is to help poor receive sensitivity or high line loss. Most good receivers will have a receive sensitivity of 12 dB SINAD on a signal that is 0.25 μV. Some are 12 dB at 0.20 μV or better. If the voltage on the antenna line (at the radio input) already meets or exceeds the radio requirements, the preamp won't do anything good. They are typically for signal loss due to high loss lines or signals filtered/trapped excessively.
You may be better off with a 5/8 wave. Do some research on the antenna takeoff angles of specific antennas you are interested in. In the same way that high gain antennas are more narrow with regard to their usable frequency, some antennas tend to radiate up and out instead of down and out.
Also, have you considered a vertical dipole? Or a loop? They are very easy and cheap to make... so you can experiment. Full wave loop antennas are true omnidirectional and fantastic with regard to receive sensitivity. I am about to build one for 80 meters after seeing a friend of mine a few miles away from me have full-quiet conversations with people I almost could hear at all.
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Hey Jones, thanks!
Hmmm, that is an interesting fact there, I am pretty sure all the RF stuff coming from that 1400 foot tower is all digital by now... so I would be willing to bet that is the reason why the preamp didn't produce more range.
This is for a simplex setup, so there is no duplexer, the preamp has a switch inside that seems to work rather well.
I've tried both ways, before cavities and after cavities, both configurations produced reduced range... so it could be as @Boxcar stated, too much gain overloading the RX of the radio...
Now that I have the preamp, I will probably experiment further with it (just got it a few days ago), and potentially moving to a 1/4 wave vertical on the mast... like @Lscott explained, it could be the elevation changes what was is killing the range... making any gain on the antenna not feasible.
Thanks and happy new year, guys.
G.
I had good luck running a pre-amp on a repeater reciever until the VHF high-band TV station on the same tower went digital. ..so your mileage may vary.
Also, when you say: "I already have two tuned cavities after the preamp", I assume you mean before the pre-amp? All filtering on the RX side should be done before it hits any amplification, so as not to amplify the noise and out-of-band stuff also.
additional cavities - pre-amp - receiver.
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Thus: Antenna feed - Duplexer -
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Power amp - exciter or Transmitter
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Hey Scott, happy new year and thanks!
Terrain is fairly hilly around here, lots of altitude changes for sure.
The interesting fact is that with the 7.8 dBd antenna it was pretty much a solid coverage 5 miles out, literally, it didn't matter if you were inside the car, inside a building, nada, anywhere within that 5 mile magic range it was pretty much full quieting on the base; now, if you passed that 5 mile mark line, it went from full quieting to it wouldn't break the squelch at all. Now, with the single 5/8 atop I can hear degradation in the signal as distance increases, and while at 5 miles it doesn't full quiet the receiver, when you pass that distance it doesn't go dead anymore...
Interesting, so for hilly terrain its better to use a lower gain antenna then, I guess that would corroborate what other users are stating.
Looks like the single 5/8 is the antenna will remain in the mast. Potentially I could tilt the higher gain antenna a bit down towards the area of interest, see if that makes any difference, giving up 7.8 dBd is hard to swallow and I can certainly tell now when we are inside buildings that before would've been crystal clear, now its super noisy, or it simply won't even break the squelch at all, but you walk outside and its good to go.
What are your thoughts on using preamps for UHF/VHF, could the lower gain antenna benefit from a 10dB gain preamp? I already have two tuned cavities after the preamp (which is off ATM)
Thanks!
G.
What does the local terrain look like around the site?
Another point to consider is very high gain vertical antennas have a narrow radiation pattern perpendicular to the antenna. General reciprocity antenna theory says the RX and TX patterns should be similar. Anyone close in will have a hard time getting into a repeater like this since the antenna is deaf if you're not in the RX pattern. Commercial broadcasters and some repeater installations use antennas designed so that the narrow radiation pattern is not perpendicular to the antenna but has a small "down tilt" angle of several degrees to compensate some what for this condition.
A lower gain antenna has a wider RX and TX pattern perpendicular to the antenna. The gain fall off is less severe. That's why you read about people claiming that a simple 1/4 wave on UHF gave them better results in hilly terrain verses using a high gain antenna where other stations are at different elevations relative to each other.
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So, I am still trying to understand why my RX range nearly tripled in range when going from a high end Diamond 7.8 dBd gain, a 5/8 over 5/8 over 5/8 (yes, a triple collinear) vertical to a single 5/8 vertical (which has virtually no gain over a 1/4 wave)
The rest of the system was identical in both cases, 15 feet 1/2 Heliax with N-connector (all trimetal), a preamp (which was OFF in both tests), two TX/RX Bird tuned cavities set with a 0.59 dB insertion loss each and 70+ dB attenuation at anything beyond 0.5 Mhz (to deal with the flamethrower uber-1400-foot-tower) and a Vertex Standar EVX-5300 radio.
So, initially I went the route of adding more dB gain to the system, first added a high gain antenna, then cavities, then the preamp, all that under the clear assumption that more dB will get me more RX/TX range, but so far it seems that the more gain I throw, the faster the RX range goes south. While the TX range is noticeably better with the 7.8dBd antenna, what I can't understand is why the RX decreases? shouldn't the RX range increase as well with a higher gain antenna?
Any help would be appreciated.
Thanks!
G.
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Been tempted about replacing the Mini-UHF on my VS radios... seems like a pretty poor connector, but then again, I could be wrong.
G.
Just solder, sometimes. Feedline disconnects, indeed feedline itself is at best a necessary evil. Why mess with it in applications where it is not necessary? For example, pop the cover from your radio and see what the board connection looks like. The fact is, the only time connector impedance really matters very much is when it is actually somewhere along the feedline. At the ends there is an impedance bump regardless of what connector you use.
I've been known to build radios (uhf included) that don't even have what most people consider an antenna connector.
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Wasn't implying that, but in some connector types that process only takes a few months, whereas other types will take years; N connectors seem to hold up a lot better in bad weather than UHF, even sealed with STUF grease, especially the outer threads.
G.
Connectors, no matter the type will always degrade as they represent a break in the electrical path and a mechanical restoration of the circuit. The mechanical pieces will ALWAYS introduce less than perfect electrical properties and a less than perfect mating of the parts, The only connection I am aware of that does not result in a break in the electrical path is a fused connection where two conductors are fused together. That doesn't imply there is no loss or impedance introduced due to impurities or misalignment in the fusion process.
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How did we land a 2nd amendment argument in a RT76 radio thread? Hmm, methinks I want to buy 155mm howitzer now...
G.
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Filters seem to be the answer to the crowded RF space... I also found that grounding the antenna and the mast helped quite a bit.
G.
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BoxCar,
The biggest issue with UHF connectors, regardless of higher frequencies impedance issues (which will reduce the power output of the radio due to mismatch), is that they are PIM magnets. Once they get dirty and corrosion sets in after being exposed to inclement weather, you'll have a massive noise generator that will take a lot of detective work to track down. I've been fighting noise on my UHF setup for months and I've finally narrowed it down to three things: LMR400 cable, nickel plating and UHF connectors. Once I moved to 1/2 Heliax, white-bronze N connectors the noise dropped dramatically. Even silver plated UHF connectors will eventually get corrosion on the threads if exposed to the elements long enough. LMR400 cable in a high wind situation is basically a noise generator for VHF and UHF, specially if its been sitting outside for a few months as well. Having the giant Candelabra tower pumping thousands of watts made the problem even worse.
RCM, so, what do you use? Magic?
heh. (j/k)G.
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Mas birra... eso eso...
G.
My chrome colored pointed hat is on, and I have my noise toys. HONK!! HONK!! rattle-rattle-rattle-HONK!-rattle-rattle. Happy New Year!
Oye Pablo! Mas Cerveza por favor!
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Thanks.
Happy new year to you too!
CrossBand Repeater
in Amateur Radio (Ham)
Posted
I have two Surecom 629s, usb and battery powered. So far they haven't let me down and I've tried a bunch of radios on them... including a TM-V71a Kenwood, a TH-F6a, Alinco MD5, BF-1801....
Distortion has happened when the input was too strong, if you max out the volume on the TM-V71a, for example, then you'll hear a mess, but you set volume back to 1/2 way and audio is fine. At least that has been my experience.
Also an excessive input level could be too much for the controller to handle over time (guess). so perhaps setting the volume to a level that opens up, and can be heard is all you really need?
G.