Lscott
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Posts posted by Lscott
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On 4/3/2024 at 4:36 PM, WSAK691 said:
There’s no spot on VHF that is even usable for this antenna. SWR is like 6+. Even on 70cm the numbers are on the high side of the usable slope. So if you bought this antenna for those purposes, it is bad. But fortunately and luckily for GMRS users, this antenna lands resonant (by dumb luck?) at the GMRS region.
My experience with a similar type I picked up cheap at a Ham swap. On the Ham 70cm band it wasn't too bad. On VHF it was VERY narrow banded to the point of being mostly useless. The SWR on GMRS put it out of the running. Oh well I got a decent magnet mount out of the deal.
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I think today will be one where Ham, GMRS and CB radio is going to get a bit of a workout. People driving around trying to beat out the traffic to find a good location to view the eclipse. With the weather forecast being crummy in some areas getting up to date viewing conditions is going to cause a lot of last minute scrambling to get to a better site.
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11 minutes ago, tcp2525 said:
I only use Transco switches. No fake specs and extremely low insertion loss.
It's not really a switch, but a coax relay. Plus it uses a 28VDC coil voltage. Not something easily available in a motor vehicle. I have a couple of coax relays but they use SMA connectors. Picked these up a long time ago for a project, but never got used.
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6 hours ago, Webslinger said:
I've seen a few comments on the Internet that a 6m band on an HT is not really that great.
That's mostly true. An effective antenna needs to be at least a 1/4 wavelength long so on 6M that would be around 57 inches long at mid band. The short helical antennas used on the radios are so inefficient that most of your power is wasted. It's the same story with those old "full power" 11M CB radio HT's. The range on them was poor.
The only thing that comes close to a useful 1/4 wave antenna on an HT is on the UHF band, Ham 70cm or GMRS. On those bands a 1/4 wave antenna is only about 6 inches long, about what the usual HT antenna size is on an UHF HT.
The antennas for 2M and 1.25M on an HT are also inefficient, but nowhere as bad as 6M.
One other point. The 6M band usually doesn't see much activity unless there is a band opening. And when it does it's typically on sideband where you'll find most of the people.
Some people claim that propagation on 1.25M is better than on 2M. I'm guessing it's due to a sort of a compromise between 2M VHF and 70CM UHF. Activity on the band ranges from nil to active depending on location. Not many people have equipment for 1.25M as it is.
If you're into Ham digital voice modes there are currently only three radios I know of that can do a digital voice mode on 2M, 1.25M and 70cm bands. Two are Kenwood, TH-D74A and the TH-D75A, which only does D-Star. The other is the Anytone D578 series, which does DMR.
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Here are a few more models. These antennas are a bit less common. The worse one to build and model was the 11 turn helix. I was looking at that for a satellite UHF down link. In the end I went with an 11 element Yagi from M2 Antennas. It was smaller, far easier to aim and the gain was about the same. The only thing lost was the circular polarization.
https://antenna-theory.com/antennas/travelling/helix.php
https://www.m2inc.com/categories/commercial/antennas/helical.html
The rest are a bit more common.
Corner Reflector:
https://www.arrowantennas.com/solid/cr4501.html
Eggbeater:
http://146970.com/PDFs/Antenna Eggbeater-Revisited-English.pdf
Turnstile:
http://www.on5au.be/Cebik-2/SomeNotesOnTurnstileAntennaProperties.pdf
https://www.qsl.net/g4hbt/dipole.htm
The Turnstile model doesn't use the "typical" dipole phasing cable setup.
Turnstile.EZ Eggebeater Rev 8C.EZ 90 deg 70cm Corner Reflector Rev 2.EZ 11 Turn Helix.EZ
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If anyone is interested in messing around with antenna simulations the software is now freely available.
I've attached some models I've played around with in the past.
Magnet Mount - Rev 2.EZ Magnet Mount Ham and MURS.EZ Ham and GMRS Magnet Mount.EZ GMRS J-Pole Rev 3.EZ GMRS 11 Element Yagi Rev 2.EZ FRS-GMRS Gnd Plane With Radials.EZ 4 Bay Anetnna MURS.EZ
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OK.
I simulated a simple magnet mount 1/4 wave MURS antenna. The frequency was selected to be about in the middle of the band. The results looks good. The match and radiation pattern look like what I would expect.
The exact same antenna was then run at a frequency about in the middle of the GMRS band, between the simplex and repeater input frequencies.
As you can see the match short of looks OK on GMRS, however most of the RF power shoots up at a very high angle uselessly into space. I guess if GMRS has satellites in low earth orbit it might be a good antenna. For normal ground work most of the power is wasted.
This is what I was getting at in my prior post comments.
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2 hours ago, WRYZ926 said:
Using power poles does make things easy and simpler. I will buy the actual Anderson brand and the correct crimper when I start switching things over. My plans are to use them for a go box.
@WRDJ205 I am going to suggest to just use the connector that came with the KG-XS20G since it is water resistant. I also suggest running the positive lead to the battery and the ground to chassis ground of your vehicle. Here is where ring terminals that are crimped and soldered is better.
For "under the hood" and exposure to weather that's a good idea. On the inside of the passenger cabin, a home setting or a sealed enclosure the power poles are a good idea.
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2 hours ago, WRUU653 said:
Is there much loss through a switch?
If you look at the photo and the specifications at the link the insertion loss is about 0.1db up to 500MHz for the example switch. That's only about 2.3 percent power loss, basically nothing to worry about.
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12 hours ago, WRDJ205 said:
To monitor the draw I bought a pretty nice watt meter. Unfortunately it only came with power poles. Guess I’ll have to either cut them off or make some adapters.
Anderson Power Poles are commonly used. I have just about everything I use outfitted with them. There is sort of a semi official configuration for them.
Anderson Powerpoles - Standard for ARES and RACES.pdf ARES - RACES Standard 12 VDC Power Connector.pdf INSERTION - EXTRACTION TOOL FOR PP15-45.pdf
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31 minutes ago, Borage257 said:
Cut it for MURS (153 MHz) and it will be pretty good on GMRS too!
If he does that it will may look OK from an SWR standpoint but the pattern will look bad with multiple lobes likely giving crummy coverage. I wouldn't recommend it other than as an experiment.
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You want a coax switch. Be sure you get one that is rated up pass the highest frequency you intend to use. Since you're stuck using SO-239 sockets on it you have to be careful to get the right insulator and socket design type.
Most SO-239 sockets for CB radio or HF work may use the crappy red or brown Bakelite insulating material around the center pin. DON'T use those!. These will cause SWR issues.
The better choice is when the material is white. That would typically be Delron or Teflon. While better than the above I would only recommend it for VHF and below.
The best is where the center pin is supported by what looks like a spoked wheel design around the center pin. That gives the interior of the socket mostly air and results in a socket impedance closer to 50 ohms, matching the radio and coax, which will mitigate SWR problems.
https://forums.mygmrs.com/gallery/image/431-coax-switchjpg/
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3 hours ago, WRQC527 said:
Wait. What?
And Midland filed for bankruptcy. Production and shipping of all models has been halted.
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20 hours ago, Santiam said:
Now I am confused, I thought the radials were a ground plane.. Interesting..
They are. It depends are what point of view you take. The minimum length for a radiating element used as an antenna is 1/2 wavelength. Obviously a 1/4 wave alone won't work. That's where the ground plane come into play. The easiest way to understand how it functions is place your finger at a right angle against a mirror. You see a reflection of your finger so it looks twice as long. The same thing happens with a ground plane. It "reflects" the 1/4wave element making it look like a 1/2 wavelength long.
By bending the radials it changes the feed point impedance so it's closer to 50 ohms, a good match to the 50 ohm coax cable. A true 1/2 wavelength dipole antenna is closer to 70 to 75 ohms with the feed point at the center. That results in an SWR of about 1.5:1, which is perfectly acceptable by just about any radio out there.
A 1/2 wavelength antenna is used where a ground plane, or room for radials at the base of a 1/4 wavelength antenna, is not possible. The draw back is the antenna is now twice as tall and the bandwidth is reduced since a special matching section is required at the base of the antenna.
Also high gain antennas are multiple sections of 1/4 and 1/2 wave elements with a "phasing" section in between the sections. Those are the small bulges or tiny single loops you see spaced along the length. The down side to high gain antennas is the gain is HIGHLY concentrated in a direction perpendicular to the antenna. Works great for relatively flat open terrain. Not so good in hills or mountainous areas. People who like to hit the trails often carry two antennas. A high gain one, these antennas can be rather tall, used when on the highway and a low gain, usually a 1/4 wavelength, when hitting the trails.
https://forums.mygmrs.com/gallery/image/259-ca-2x4mb-jeepjpg/?context=new
https://forums.mygmrs.com/gallery/image/268-ca-2x4sr/?context=new
https://forums.mygmrs.com/gallery/image/338-cheap-14-wave-gmrs-antenna/?context=new
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1 hour ago, WRYZ926 said:
You can roll up any extra coax at the antenna end which will act as a RFI choke, but it shouldn't be necessary.
For a J-Pole type antenna a coax line choke at the base of the antenna is HIGHLY recommended.
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Your comments about signal penetration is generally true.
The 2M band is popular for general communications. It’s other advantage is Hams are the primary users and enjoys worldwide allocation, typically 144 to 146 and 144 to 148, depending on country and zone.
The Ham 70cm band, at least in the US, is allocated frequencies from 420 to 450. There are some reductions in spectrum when close to the Canadian border. Due to the large spectrum allowed you find various experimental modes being used. Also most of the digital voice activity is on this band.
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33 minutes ago, Guest IDontKnowAboutRadios said:
For the use case, our main job is working on and maintaining oil/gas wells
Oh-oh. The recommendations just changed. That’s an VERY important point. For safety reasons, fire and explosion, you would be well off to get what are called “intrinsically safe” radios. This might actually be a requirement for your work environment! They are specially fitted normal commercial grades radios but have been specifically sealed to prevent any arcing or sparking from the radio’s internals which can precipitate a gas explosion or fire. The same also applies to the battery packs, external speaker microphones etc.
If you look in the Kenwood catalog they do sell that type of radio for the models I recommend along with the safety rated battery packs.
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Kenwood offers some very good radios for a reasonable cost. For rugged outdoors use as you mentioned a public safety grade radio is a must. I would recommend the VHF models in the attached brochures. You will need the software and license for them.
To add some of the digital voice modes to the higher end models requires additional licenses.
The NX-5000 series is the only one that can do three digital voice modes, two at a time, NXDN, DMR and P25. The licenses for the first two are really cheap, about $42 each. The P25 license is very expensive and typically used by government agencies and first responders like police and fire.
If you don't need P25 then the somewhat cheaper NX-3000 series hand held might work for you.
The cheapest option is the NX-1000 series. They are good radios but aren't really public safety grade.
Encryption options are available for some of the digital modes if required.
The attached catalog has all of the options listed and the current "list" price. You may qualify for a discount if you're a local, state or federal government agency etc.
Kenwood Land Mobile Radio Guide 2024.pdf NX-5200_5300_5400.pdf NX-5700, 5800, 5900.pdf NX-3200_3300.pdf NX-1200_1300 Num 1.pdf NX-1700_1800.pdf
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1 hour ago, WSCA349 said:
Newbie question here. For example, I am monitoring on Channel 23 and someone is transmitting on that channel but yet I hear the responding person on say channel 21. I have a dual band handheld (UV-5G plus). Is that normal?
How have you got your radio programmed up?
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Despite the government's denials, a cell phone kill switch, I'm sure in the case of some "domestic disturbance" cell phone use would be restricted or disabled completely by their order. After J6 if it didn't exist then I'll bet it does now. That's when you're likely to need your radio the most to coordinate with others to get out of an area to a safe place.
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1 hour ago, WRYZ926 said:
Again use quality coax and quality connectors (if making your own cables).
I've tried installing my own connectors, wasn't easy, didn't turn out that well. Unless you've done a lot of it, and have the right tools, it's money well spent to just buy a cable with the connectors already installed. One less question mark if things don't work as planed.
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38 minutes ago, nokones said:
t's just 1 dB, not significant and you won't know the difference in the operating distance unless you buy your cable from Amazon.
For a db or two that's true for most people. With a modest gain antenna the coax loses can be compensated for. For people on the very fringe of a coverage zone every db counts.
Best stationary antenna?
in General Discussion
Posted
You need a few more zip-ties on the cable. I imagine that's to try and take the weight off the cable connector at the base of the antenna.