fremont
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Posts posted by fremont
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I was troubleshooting a 25' length of RG58 today that had continuity where it should (hot to hot; ground to ground; no shorts) but wasn't receiving RF. I put on a 50 ohm dummy load and connect to my analyzer and SWR was off-the-charts so into the garbage it went.
As a control, I hooked up a 2' RG58 jumper (with dummy load) and saw the expected 1:1 at the lower bands; however, when I tried at GMRS frequencies, it was 1.9:1 with 25 ohms. Helped visualize the coax loss we often attribute to antennas in the UHF band.
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Purely anecdotal, but I and a friend have tried MURS vs GMRS in high desert country (no buildings or big mountains, etc), and MURS wins at 2w vs GMRS at 5w. He lives there year-around and had no idea what MURS was until I loaned him my Wouxun KG-805M (and a Smiley OEM antenna). He said "Thanks, I'm buying two of them."
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Is it possible to get COR/TOR out of a TK-880 via a homemade cable with a RJ-45 jack? Or, do you need to disassemble the transceiver and solder? This implies the latter but wanted to ask first.
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Lots of off-grid outdoor enthusiast GMRS users who would benefit from APRS (e.g., knowing the location of their party, allowing SAR to find them). I personally think APRS (or a variant) finds its way into GMRS.
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In addition to the 144.390 "problem"
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Quote
<<chewing fingernails>>
Best thread ever.
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6 dB is one S unit..... just sayin'
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I don't have a permanent installation, but, when camping, hunting, etc, I'll usually put up a Nagoya 200-C as we also like to tinker with MURS too. Or, if I'm lazy, my Ed Fong DBJ-GMRS tuned to 465.
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2 hours ago, OffRoaderX said:
You might also consider a repeater that has a high-temperate rating. My VXR-7000 is rated to operate at up to something like 160F (if i am recalling correctly). The thing is nearly bullet-proof..
Looks great; however, discontinued. BTWR's version included duplexer + programming. Is Vertex coming out with a new model?
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1 hour ago, WRQC527 said:
Just curious, I'm guessing some kind of storage battery setup? Obviously the total draw of the repeater and any peripherals will factor in to the capacity of the battery system and the solar panel output.
Haven't gotten that far.
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1 hour ago, Sshannon said:
If you use a low powered repeater in a box like the Retevis RT97S or Midland, the entire repeater is in a waterproof enclosure.
Otherwise it’s going to depend on what repeater you use. There are NEMA enclosures that can be mounted on your tower or you can build something.
Air circulation, even when the ambient temperature is 100° is still better than stagnant air that allows components to build up even greater heat.
NEMA enclosures can be outfitted with air conditioners but everything you do that increases the energy requirements makes things more complicated.
In addition to protection from the elements, it's also to try and discourage theft in case someone comes across the site.
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Some friends and I are looking at building an offsite GMRS repeater on someone's remote property using solar power*. Two questions were currently pondering:
1. What do people use for a "vault" to secure radios, duplexer, etc?
2. This location can reach > 100F in the summer. I concerned a fan will only blow around hot air. Low duty cycle, though, with traffic picking up during hunting and snowmobile seasons. Any thoughts on temp control in whatever vault we use?
* We haven't yet run the math on power needs yet.
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I was cleaning up my shop and stumbled across my first GMRS radio, the BTech GMRS v1. In thumbing through the manual, I saw it supposedly offers tone scanning, but I've been unable to get it to function as described in the manual.
I'll have an active conversation going on some repeater and I follow the attached directions, but I never get the CT icon on the screen nor does it start scanning through possible CTCSS codes.
Operator error I'm guessing, but I'd appreciate a hand if anyone has successfully done it.
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1 hour ago, KAF6045 said:
Still not usable as MURS - as modeled - with a 25:1 SWR, but it does have a nicer pattern for reaching the horizon.
Interesting work-up. 155 MURS is 1/2 wave for this antenna. I'm getting <1.5 SWR at the commercial Blue/Green MURS frequencies with 6" 90 deg radials.
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3 hours ago, KAF6045 said:
If using enough radials, you could try cutting half for 467MHz and the other half for 462MHz.
Total of four and there's only 1/8" difference between 462 and 467. I've bent the radials to a 40 deg angle in an attempt to best match impedance. Feels like splitting hairs at this point, however.
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This antenna is 1/2 wavelength at 155 MURS and 5/8 at 460 (e.g., GMRS). I am going to use it as a base antenna on top of a NMO mount. For GMRS, it'll primarily be used for simplex communications, but there will be instances whereby it'll go through repeaters.
I had a couple of questions--which I subsequently tested: 1) Would the GMRS (5/8 wave) frequencies benefit from elevated radials and, if "yes," then 2) how long should they be? Question #1 gets debated a fair amount from what my cursory review of the interweb uncovered.....it seemed as the antenna would benefit from some type of radial. To answer Q #2, I went to this website to get the radial length. (By entering 465.200--halfway between GMRS duplex Tx and Rx frequencies, I was given the answer of 6" radials. I cut mine from 1/8" alum. rod.)
The results on MURS (155)--again, a 1/2 wave antenna at 155--were consistent: The commercial (Blue4, Green5) channels near 155 performed better than Ch 1-3 near 152, with SWRs of 1.35 and 2.19, respectively.
For UHF, including GMRS, the results were interesting. By adding the radials, the SWR graph became the traditional very steep parabola which helped the UHF frequencies especially near repeater inputs, e.g., 440 (3.05), 445 (2.35), 450 (1.84), 462.800 (1.55), 465.200 (2.06) and 467.600 (2.68). Without radials, it was a mildly meandering, relatively flat but downward sloping line, e.g., 440 (2.98), 445 (2.54), 450 (2.36), 462.800 (1.95), 467.200 (1.59), 467.600 (1.64).
So, I concluded that I would use the radials, since a) I want to use the antenna to hit both FM and DMR UHF repeaters and b) the majority of my GMRS QSOs will be via simplex. The antenna is definitely tuned for what it says on the label: 155 and 460. Not 155 and 465.
Does this sound right to the RF engineers of the world?
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On 8/4/2022 at 3:40 PM, KAF6045 said:
I really don't think you will find one antenna that is tuned for both 2m Amateur AND GMRS. They will either be Amateur 2m/70cm OR commercial 155MHz/465MHz.
Tram 1181 may get you close. (SWR) from a fender mount:
VHF 144.000 (1.34) climbing up to (1.62) at 148.200
UHF (2.05) 440.000 / (2.29) 443.333 / (1.82) 446.800 / (1.55) 450.000
GMRS (Approx. 2.00) in 462.xxx frequencies and (1.36) in 467.xxx repeater Tx frequencies
MURS (2.06) Channels 1-3; (2.35) for Blue/Green (Ch 4-5)
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I know this post is late to the game, but I use the Nagoya NMO-200C (tuned for 155/460) and it's been a good unit.
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I wanted a monoband VHF antenna which I could use at hunting camp for both ham VHF frequencies as well as MURS. Decided on the Diamond M285. (I got the M285SNMO model as my mobile-to-base bracket is a Tram 1465 with a NMO-to-UHF mount.) This antenna is intended to be tuned and comes with a cut sheet. Originally, I wanted to cover starting at 144 MHz through the entire MURS band up through Blue/Green at 154.600, but I found I couldn't get there without wiping out too much of the ham band. (It's about a 7 MHz range to maintain less than 2.0 SWR.) I ended up cutting off 2" from the 47.25" antenna and ended with a midpoint (lowest SWR of 1.18) around 148.853. Used 20" radials on that Tram bracket. Eager to try it in the field.
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I have a CCR purchasing habit which, until I'm broken of it, I'll likely keep buying Wouxun. This includes GMRS, MURS, and ham HT's. A large part of this reasoning is that I have their programming cables, and the software is readily and easily available from my preferred vendor (BuyTwoWayRadios.com). I'd offer that this may make your life easier if you broaden beyond GMRS. Good luck.
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38 minutes ago, tweiss3 said:
I have one in route to try with my 705.
Yes. The "JeepBangkok" handle is a tough one to forget.
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On 2/18/2022 at 5:33 PM, WRPH745 said:
I also found:
The Comet GP-15 is a triple band on 6 m / 2 m / 70 cm.
The Comet GP-6 is a double band on 2 m / 70 cm.
I know the best thing would be to get a GMRS antenna and an antenna that would cover the 2 meter band. To keep down expense and only running one line into the house I would like to just get one antenna to cover both GMRS and the 2 meter band. It is my understanding I cannot put a GMRS antenna and a 2 m antenna on the same mast. If I could I would be tempted to get a separate antenna just for GMRS.
So I am leaning towards a double or triple band antenna and trying to pickup GMRS using the 70 cm band. All the antennas listed have similar price points and similar specs for similar bands.
Is there any reason to get the double rather than the triple?
If I should go with the triple which triple? At this point I don't have enough knowledge about 6 m or 1.25 m to know which way to go.
I have a Comet SBB-15 mobile tri-band antenna (2m/70cm/6m) that I am trying to use as a base unit (camping, etc) utilizing a Tram 1465 mobile-to-base bracket. The Tram bracket came with ~20" radials which work fine on 2m/70cm but not 6m. I'm currently beginning work on cutting longer radials (first trying 1/8" aluminum rods at around 60") to use on 6m then run through an antenna analyzer to see if they'll work at all on 6m and, if so, whether they will on 2m/70cm as well. I kind of doubt it, which then kicks me back into the possibility of taking two sets of radials along which is a real pain if I'm going to want to work anything beyond 6m. I have a mobile in those bands, so I thought I'd try setting it up as this base, too, but it's feeling a little like a pipe dream at this point.
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On 2/23/2022 at 1:07 AM, MichaelLAX said:
How long is the 6 meter telescoping antenna when fully collapsed and when fully extended?
Sorry, just saw this. 9" closed; approx. 47" extended.
- tweiss3 and MichaelLAX
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2
Lossy RG58? An experiment
in Technical Discussion
Posted
I'd have to double check but I'm pretty sure it's up to 500 MHz