Lscott
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Everything posted by Lscott
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I’m glad I don’t own and operate a functioning repeater system. I don’t need this kind of headache. -
You can look at the attached data sheets. The down tilt is spec’ed at zero I believe. DB408-B Product specifications.pdf DB404-B Product Specifications.pdf
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I think it means about the same thing. Yup, the tilt is done by altering the phasing of the elements a bit. I think it could be done by changing the length of the cable between the elements, or the element spacing, which likely will affect the match to some degree. Myself I wouldn't try messing with it. You need really good equipment to measure the field pattern and or simulation software to see the effects.
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The antenna you mention in the title shows a "beam" tilt of zero degrees in the attached datasheet. I think you'll have to find another solution. DB420-B.pdf
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I'll bet it did.
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From the album: Misc. Radio Gear
This is a very simple 1/4 wave ground plane antenna. It's mounted on a cheap baseball cap using a zip-tie. I wanted something simple to use at swaps to get the antenna up in the clear and away from the body. Looks weird but works very well. The SWR is low enough the antenna is usable over the entire Ham 70cm band and up through GMRS. The antenna is built using a BNC PCB male socket with thick bus wire soldered on for the ground plane. The vertical section is thinner wire. The wire elements are only about 6 inches long making this ideal for a compact antenna. A 90 degree BNC male to BNC female adapter is screwed onto the bottom of the socket. I used a short cable with BNC male to SMA adapters to connect to the antenna and radio. The radio was kept on the belt and used with a speaker microphone. The antenna was modeled using EZNEC V7. https://www.eznec.com/ The tested results are very close to the model. The measured SWR is a bit lower due to the slight attenuation in the 3 foot jumper cable. The radio I used was an Kenwood NX-1300DUK5 set at 1 watt, low power, using DMR. That kept the effective power to around 0.5 watts due to the nature of DMR, TDMA, modulation. With the error correction I had clear copy just about everywhere. I used this while at the annual Hamvention held in May. -
I hope it doesn't mutate in another cell phone store. At the end the local Microcenter computer store had more electronics parts for robot builders in one section than Radio Shack had in the whole store.
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Then turned in to "cell phone shack." Then went bankrupt. I did hear they might be coming back in a few areas. I also remember going to Lafayette and Olson Electronics as a kid. They're gone too. Heath Kit is kaput. Lots of kids, and adults, got their first exposure to electronics building their stuff.
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Use to be able to go to Radio Shack, Best Buy etc and they had rolls hanging on the display pegs in the TV accessories area. I think If one wanted to build a Slim-Jim I would try the 450 ohm ladder line. That's what the N9TAX ones use.
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The RigExpert antenna analyzers are nice. The main attraction I have for them is the scan function. As a Ham you don't operate on just one fixed frequency. It's important to know what your antenna tuning looks like of the range you are going to use. I built one of the cheap 300 ohm TV twin line J-Pole antennas just for fun to see how well they work. These are the type recommended to have newbies build because they are simple to make and usually work well enough for an HT indoors or out on a field trip. The SWR is also reasonable. You ABSOLUTELY need the RF choke at the base of the antenna. I just used about 10 to 15 turns, single layer, of RG-58 rolled up on a 1 inch wood dowel pin. Good luck trying to find 300 ohm TV twin lead now days. Oh well. http://hamuniverse.com/2meter300ohmslimjim.html Antenna Scan Results (2M Roll Up Twin Lead).pdf
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I used the Rigexpert AA-1000 to make my measurements. The antennas are a bit sensitive to the environment where you make the measurements so I’m not a bit surprised by slightly different results. Also the antennas are all hand built and tuned. That can result in differences too. I haven’t heard good comments about the Surecom meter. Most are about the same as yours, inaccurate results. But people like them and they keep selling.
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I did a test on the N9TAX antenna a while ago. It’s similar to a simple Slim-Jim. The SWR isn’t outrageous on the GMRS frequencies. There are two versions. One tuned for MURS/GMRS. The other for 2M/70cm. N9TAX-MURS-GMRS-VHF Scan.pdf N9TAX-MURS-GMRS-UHF Scan.pdf N9TAX-2M-70CM-VHF Scan.pdf N9TAX-2M-70CM-UHF Scan.pdf
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Is it the ProTalk version?
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That’s nothing to worry about. You can use the antenna full time with that SWR ON GMRS. Most radios don’t start having issues until the SWR is 2:1 or higher.
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That would be a nice feature to have on a radio. Maybe not at the end of every transmission. There is a feature on one of my digital radios to do it. But it has to be manually initiated through one of the menu selections every time I want to send it. Not very convenient.
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Surecom SW-102: What it tests, how it tests
Lscott replied to Webslinger's question in Technical Discussion
Also consider the environment a typical HT is used in. hand-held, mobile with external antenna, hanging on a belt, stuck in a utility vest pocket. All those will really screw up the SWR. I was looking at the spec's for some of the hybrid RF power blocks used in many HT's and some mobile radios a while back. The HT one's I've seen they're rated to work up to a max SWR of 20:1!! Basically no antenna. It sort has to be that way due to the highly unpredictable environment HT's have to work in without failure. See example file attached. Look at the first page at the bottom. M67799MA.pdf -
Surecom SW-102: What it tests, how it tests
Lscott replied to Webslinger's question in Technical Discussion
A 50 ohm dummy load will give you a perfect 1:1 match, but nothing radiates from it.
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Mobile antennas and high gain = not always best?
Lscott replied to SvenMarbles's question in Technical Discussion
This is why some people keep a couple antennas in their vehicle. They use a low gain, 1/4 wave, in very hilly or mountainous area or a high gain antenna in nearly flat areas. -
Tidradio TD-H3 "Stun" and "Kill" functions?
Lscott replied to WSAA635's question in Technical Discussion
This is getting a bit off topic and into the weeds a bit. But the rule specifically mentions equipment certification. Anything after the cutoff date will not get certified if it has any kind of voice obscuring features. However it’s silent about equipment that was certified before that date and no mention the feature must not be used in that case. So, it’s very possible voice scrambling in OK, BUT only on radios certified before Dec 27, 2017. So, my favorite Kenwood radio, TK-3170, I use for GMRS, which by the way is certified Part 95 in 2004, has analog voice scrambling so it could be legal to use that feature. Interesting thought. -
https://3fs.net.au/tropospheric-propagation/
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Sargent Schultz, I see nothing.
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Manufactured by Gollum Radios I'm guessing.
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I'm not a conspiracy believer, but either the government has a secret "kill switch" or an understanding with the cell phone companies to turn off the service when asked/ordered to do so. If nothing else the FCC has the authority to license and control transmitters, which of course includes cell phone towers, and force the shut down. People forget that Ham radio was shut down during WWI and WWII by the FCC. It took a lot of lobbying to allow Ham radio to resume in a fashion like it was doing before the war. Not likely today, but that could change. https://bw.billl.net/wp-content/uploads/2019/11/Radio-History-03-Amateur-Radio-Before-and-During-WWII-By-Dan-Davis-W8LUX.pdf Then there is the question what happens to the Part 95 services? Is it also possible they too might be ordered to cease operations?
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Just think about what if the government wanted to pull the plug on purpose?
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Could also be some mixing products in the radio's front end. Take a frequency on 931.6MHz (public safety frequency) and mix it with 469MHz (business frequency) you get the difference of 462.6MHz right in the GMRS range. It could also be just the radio. My Kenwood dual band TH-G71A shows a full scale signal on channel 7. Take the antenna off, nothing. Then I tried several other radios on the same frequency. They show nothing there. So apparently it something weird with just the one radio.
