WRNA236
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Posts posted by WRNA236
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I've read that the T800 has X-Pand but the fella who started the RadioReference thread says it seems less offensive. I wonder too about the T400, which was what I was considering as hand-out radios since high power on them is 1.7 watts according to the FCC test data in their grant. The T600 and T800 are listed as 0.75 watts in the FCC grant.
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I use an Iota DLS-45 and 100 A-hr battery exactly in the way you describe, as essentially a UPS for my radio station. The DLS is technically a battery charger (it needs a battery, it won't stay in regulation without one) but will supply current like a power supply when asked. So the normal mode is the charger is in float on the battery, which is considered stand-by in UPS terms, with it supplying current up to it's rating, 45 amps in my case. If you exceed this draw the battery would have to make up the difference. If the mains go away the battery supplies all the power and the output of the DLS is sufficiently high impedance as to be essentially present no load.
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35 minutes ago, WRNA884 said:
I would not use that mount and damage your paint in anyway. That'll turn into a rust spot.
That is the downside to those lip mounts. When they work well it's because you've successfully gone through the paint into bare metal for good conductivity.
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2 hours ago, axorlov said:
I'm going to state it again: HT to Mobile with 1/4-wave at 6 ft on a flat roof has 4 times the range (I'm being conservative) of HT to HT. In some cases significantly more, like in rocky canyons. Witnessed, tested, proven. Besides the wave absorption (line of sight, obstacles, yada yada), there are wave interference, diffraction, reflection and scattering are taking place.
That is all true, of course, if you do not use Baofeng. With Baofengs on both ends courier on a bicycle provides much more reliable comms.
I'm going to agree again, I believe you. An HT is suboptimal.
The 4 foot to 6 foot part was to the point made about a portable tower. Moving an antenna two feet up to your roof can't going to break the laws of physics or uncurve the Earth. You can sometimes get a tropospheric duct or other oddity like a weird diffraction to see over the horizon but you can't count on that from an emergency comm standpoint. And in the case of a tropospheric a 200 miles path isn't much use when you need 10.
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1 hour ago, Coffeemaker said:
All true, but we don't work in Chattanooga often (once). We need communication from our work base to several work crews in the field and from coordinator to coordinator. Sites are most often some random town in TX, LA, or FL. We'd have to have an amateur operator sitting/working with each crew and at the work base. Once the cell systems are repaired, phones work better, but until then, we'd like to be self sufficient.
Gotcha. I was just basing the TN ARES example on your call sign. Most States and counties have an emergency management plan that's similar, though. Do you work with FEMA and local agencies (e.g. within some sort of NIMS/ICS structure) or is it a stand-alone situation?
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30 minutes ago, axorlov said:
In my personal experience, using mobile with 1/4-wave on a flat SUV roof at least quadruples the range of HT to HT.
And regarding Baofeng (Btech, Pofung) - stay away from these. In a disaster situation you need your radio to actually work, with extended duty cycles, with interference from other radios nearby.
There is indeed two factors at play.
Foremost you are 100% on point about maximizing your station's potential and getting a good antenna on a good ground is paramount. No HT is going to be ideal and even if it's radiating well just the fact that it's being held by a bag of meat absorbing RF at a bad angle is going to cut your range. That 5 watts is doing more work warming you up than radiating useful signal.
The original point was line of sight.
Two HTs at 4 feet can expect a range of about 5.6 miles (2.8 miles each) absent any obstructions. Moving one station to 6 feet high increases this to 6.3 miles (3.5 miles plus the HT's 2.8), so less than 1/2 mile improvement. Putting your trailer antenna on a crank up 30 foot tower increases this to 10.6 miles (the 30' tower will now have a range of 7.8 miles).
The original point is valid, though. Going from an HT at 4 feet to a truck roof at 6 feet isn't going to make much difference in increased coverage and especially when you're blocked by terrain and buildings.
If there's houses with roofs 15' or 20' high the handhelds and mobile still won't go more than city blocks while the antenna on the 30' tower will be more likely to work out to at least a couple of miles since it's eliminating half the obstructions. Getting an antenna into the clear makes a big difference. This is still true with an HT. Having one HT user simply walk up a hill or stand on the roof will do more than pushing more power into a perfect antenna on your truck roof if you're between buildings.
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The reason a 1λ antenna isn't common is the radiation pattern is starting to develop odd lobes.
Physically and electrically an antenna has to be some multiple of the wavelength at your frequency but not all multiples produce the same result. The baseline 1/2λ dipole or 1/4λ monopole (half a dipole where the other half is ground) produces a pattern that's generally uniform and has one primary lobe and has a characteristic impedance that's easy to match with a radio and coax.
We tend to use 1/2λ and 5/8λ monopole antennas because they show gain without a ton of oddity or artifacts. These lengths aren't difficult to match so they're worthwhile trade-offs.
Other lengths are difficult to match or practically longer without offering much benefit. The little bit of gain in the lobes you get with a 1λ over a 5/8λ comes with a couple of significant nulls which will result in fading as the whip flops around. That means it'll go from strong signal to weak annoyingly, so it's not a preferred mobile configuration. The upside is a 1λ whip can be matched like 1/2λ.
FWIW, I use a slightly long for the 2m ham band 1/4λ whip with a diplexer for VHF APRS and GMRS, which means my antenna is actually 3/4λ. Odd multiples match the same so a 1/4λ for 150 MHz will be resonant (and the same impedance) again at 450 MHz, 750 MHz, etc. just with the increasing number of lobes as the whip becomes several wavelengths long.
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11 hours ago, MacJack said:
I think you all have good comments... the way I see it is GMRS is for your family, farm and neighbors who have a license and permission to talk on your repeater. Ham is more local, regional and national. Now I do like Zello to talk with others in the USA. I have made several new friends in remote places.
Yes I have my Ham ticket and really only use it to speak to local club members in the club repeater. You just have to find what you want to do to serve others and go for it.
MacJack
Certainly can see where GMRS has a place in your individual disaster plan potentially. At a family or neighborhood level it could very well make more sense to use it since it requires no test and is much less of a hurdle to get everyone on board.
The reason I bought up ham was it sounds like the original poster is talking about providing emcomm for an organization which requires some imposed formality if not actual conformity with Red Cross and FEMA training, procedures and infrastructure, which local amateur radio groups may have already in place. So while he may have to get his ticket but that opens up a huge world of options.
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[deleted]
- WRMH343 and maddogrecurve
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2 hours ago, wayoverthere said:
Interesting, I also may have jumped the gun then...i'd be curious how their certification dates compare to the implementation dates of that presentation and/or revised wording in the code, and whether theyre certified under 95a or 95e.
Just spot checked a few IDs and their FCC listed ranges. The only non-95 I knew was the TK-3170 but I can't say whether it is ever used for GMRS or not. Does seem to support the intent to not grant 95 for radios covering amateur bands. These grants date back prior to 2017 I think in all cases. Anything newer than this will be likely not submitted by Kenwood/Vertex/Motorola and might not be strictly the book (e.g. suspect for use as reference). Midland probably submits valid data but they wouldn't have any models with the necessary features for consideration.
Kenwood TK-3170 ALH34713130 400-430 22, 74, 90, 90.21 Kenwood TK-3180 ALH37333110 450-490 22, 74, 90, 95A Kenwood TK-3130 ALH33293110 460-470 90, 95A Kenwood TK-3180 ALH37333110 450-520 22, 74, 90, 90.210, 95A Kenwood TK-3200 ALH36923130 450-470 90, 90.210, 95A Kenwood TK-3230 ALH383200 460-470 90, 95A Kenwood TK-8150 ALH32283110 450-500 90, 90.210, 95 Kenwood TK-8180 K4437313110 450-520 22, 74, 90, 90.210, 95A Kenwood TK-8180-H K4437313210 450-520 22, 74, 90, 90.210, 95A Kenwood TK-860H ALH29383210 450-490 22, 74, 90, 90.210, 95 -
2 hours ago, Hasaf said:
I am also glad I came across this thread. I am getting ready to drill my FJ Cruiser instead of the lip mount that I am using. I was looking at these. I have a Nano VNA, I have no idea which version. So far I can't say I am too happy with it. It is extremely small and hard to read, that said, this is the best Nano VNA SWR video I have seen.
This is just a rough look at the ones I have looked at.
MFJ-894 1.6-525MHz 2, 20, 0200 159.95 Large twin needleMFJ-864 HF/VHF/UHF 30, 300 129.95 MFJ-817 144/220/440 30, 300 129.95 MFJ-849 HF/VHF/UHF 200W 199.95 Large Digital MFJ-867 144/220/440 400W 189.95 Large Single needleMFJ-873 125-525 200 W 99.95 SW-102 125-525 125W 56.99 Positive reviews on mygmrs.comDaiwa 501 140-525 200W 105.99 Positive revirws Daiwa CN-901 140-525 200W 155.99 Dual needle large display High qualitySaw your list. I have a MFJ-864 SWR/power meter on the test equipment shelf. It does the job but it's certainly not a rugged piece of equipment so I'd caution not to use it as field gear very often. It's intended to be used in your shack and even there it doesn't really inspire confidence. It's like most things MFJ, which do the job and often fill a role at a price we cheap hams can stomach. However they are the textbook example for "You get what you pay for" most of the time. I'd personally go with the Daiwa 501 if you don't need HF coverage.
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On 6/15/2021 at 11:55 PM, wayoverthere said:
so...one other tidbit i noticed when reading poking around 95e (https://www.law.cornell.edu/cfr/text/47/95.1761) is (c), which seems to imply 95e/90 dual certification is still POSSIBLE, but can't overlap with ham (being a non-certified service).
also found some interesting (good) suggestions on radioreference, for text to go into 95.1735, since that section is currently "reserved".
This document is often referred to support what you're saying.
https://transition.fcc.gov/oet/ea/presentations/files/nov17/54-Part-95-Misc-Eqpt-Filing-r1-TH.pdf
Attached the 3 mainly relevant slides regarding GMRS.
In the notes the OET says
QuotePer n149 of FCC 17-57, the preceding serves to “clarify” the preceding/replaced 95.655(a):
– n149 Several commenters are concerned that the proposal to prohibit combination radios would prevent GMRS licensees from using surplus Part 90 equipment in GMRS. ... This is not our intent. We will continue to certify equipment that meets the respective technical standards for Part 90 (land mobile) and Part 95 (GMRS) in both services, if requested. However, we are amending the language in new section 95.1761(c) to clarify the requirement in old section 95.655(a) that Part 95 GMRS radios will not be certified if they are equipped with the capabilities to operate in services that do not require equipment certification, such as the Amateur Radio Service.
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18 hours ago, okinater said:
I believe one ribbon is for the KRK-10 and the other is for a front mount configuration.
I have a TK-8180 and KRK-10. The stock ribbon cable between the face and body was part number E37-1120-05 and has description of FLAT CABLE (30P/TX-RX). You leave this ribbon in place and add a couple of folds when installing the KRK-10. The kit includes a new ribbon for the face side of the kit.
Either way the description matches close the Pacparts part number 880H04-8897-72 which has description of Flex Cable (Display - Tx/Rx), that substitutes to 881H04-8116-92. It also looks the same as the original ribbon, which has no folds originally.
The other ribbon shown in the service manual is E37-1110-05 and is called FLAT CABLE (30P/D-SUB). That connects the 25-pin D-Sub on the back to the PCB in the body. That description matches the other cable part number 880H04-8887-72 Flex Cable (Tx/Rx - D-Sub) that subs to 880H04-8115-72.
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7 minutes ago, kidphc said:
Funny enough swapping to a 10m hamstick netted 1:1.12. Well till it fell off on the highway and got run over.. now it is a bit higher. Lol
Sent from my SM-G975U using Tapatalk
Hamsticks can show a closer to 1:1 due to their nature as shortened physically but 1/4λ electrically. So there's some coil loss. They have the same ground limitations as a full length antenna, though.
BTW, remember SWR is logarithmic. So 1:1 means no reflection but 1.12:1 is only 0.32% reflected. IOW 100 watts in and 0.32 watts was reflected. At 1.5:1 you see 4% reflected, 2:1 reflection is about 10% and 3:1 about 25%.
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Don't get too wrapped around the axle watching SWR. It's one aspect of tuning an antenna. It's important but having an absolutely perfect 1:1 SWR is no guarantee of a good antenna. A purely resistive dummy load will show 1:1 VSWR but radiates essentially zero RF energy. An incandescent light bulb will radiate more RF while showing a terrible SWR than a dummy load.
For example, a 1/4λ monopole has a characteristic impedance of approximately 36Ω and thus a SWR that calculates to 1.38:1 when it's perfectly tuned for resonance with a 50Ω feed and actually exciting electrons well. In the real world a SWR from 1.1:1 to 1.5:1 for such an antenna indicates a very good antenna when you figure in non-ideal ground, coax loss, etc.
In the impedance plot and Smith chart you'll see the effect of everything, the connectors, the coax, the antenna and its ground. That's the advantage of using a VNA or even just an SWR bridge or antenna tuner like the MFJ is that you can see the dip and trends. Point being it allows you to see if your measured values jive with your expected values.
Point here is 108" (102" plus a 6" spring) is very close to 1/4λ for 10m (it is on 11m) so that you got 1.7:1 is actually about what you would expect. It'll never be 1:1 and if you get that it means you've added something that's absorbing energy to make it so, e.g. the capacitance that's been suggested.
That's essentially building a matching network that's unnecessary in this case. If the antenna itself was not resonant or had a very high impedance (such as a 1/2λ end-fed, which has a VSWR of around 2kΩ at resonance) you have to impedance match to your radio. That's just what you have to do. But the matching network doesn't make the antenna any better, it just makes it so the 50Ω output of the radio doesn't see a big reflection that will cause damage or kick in protection circuits.
But this is not necessary here. Your radio will have no trouble with a 1.7:1 SWR. It won't start to roll back power until about 3:1 in most cases and at 1.7:1 this antenna will be radiating all the energy it's capable of. Like I say, your measurement validates what you expected. Any matching will just be consuming energy and not helping make the antenna any better necessarily.
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On 12/1/2020 at 6:16 PM, 1URFE57 said:
I have no problem with mobile antenna that has 136-174 range I encountered a few with 136-174 range that have been center tuned at 145.000 manufacturers do this for SWR purposes.
Make sure to read the specs and measure the antenna. A VHF antenna with 25% or 38 MHz of usable bandwidth is pretty unusual. Bandwidth is defined as the range of frequencies where the antenna will show 2:1 or less SWR and a more typical bandwidth is on the order of 10% (that's the rule of thumb for a plain 1/4λ whip over a good ground).
So this probably means the antenna can be tuned in the range of 136 to 174 and they've centered it at 145 MHz from the factory to be sold to ham customers. The same antenna might come tuned to a different center (or just not tuned) from a commercial supplier.
It's possible this particular antenna does actually have such a wide bandwidth but the radiation efficiency will be very low, meaning it's not going to perform all that well on the air with a lot of loss in the matching network. The devil's in the details. You generally can't have everything, so wide bandwidth comes at a cost in performance.
But since you're presumably after a ham antenna for 2 meters we really only need about 3% bandwidth to cover our whole allocation of 144 to 148 MHz.
Dual Band Amateur Antenna Side Mounted to GMRS Antenna Mast
in General Discussion
Posted
That's a really slick way to do it. Very inventive!
Just a general FWIW statement, don't neglect the benefits of vertical separation. Antennas don't radiate necessarily in perfect 180° spheres and the more gain they have the more flattened their patterns become. There's a zone where the two might interact (which is the principle behind collinear elements) but it may not take much vertical distance to fairly effectively decouple them.
Just ferrites chokes I wouldn't think will be enough to filter 70cm ham from GMRS. They are effective for gross filtering, e.g. keeping a feedline from becoming an antenna or preventing a 20m station from affecting your 70cm. They might be enough to keep VHF and UHF from interfering with each other, maybe.
Ferrite chokes are several tens up to even hundreds of MHz in bandwidth. So they can't substitute for true in-band notch and pass filters or at very close frequencies, cavity filters. The good thing is it's doesn't have to be difficult or expensive to build and test. Even simple coax 1/4λ stubs might be sufficient.
You might find this approach interesting since it only requires coax to test: http://www.radagast.org/~dplatt/hamradio/K6OIK-filters.pdf
The fallback is to pull out some caps and get to winding coils. It shouldn't be necessary to use cavity filters, although at 50 watts you might be looking at needing pretty hefty attenuation just the same.