Lscott
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Posts posted by Lscott
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29 minutes ago, tcp2525 said:
A question for all you gurus out here. I'm dealing with the antenna in the title that is up about 100' that performs perfectly in the northerly direction, but sucks going south. The hill I have to go over really isn't overly high, but high enough to attenuate an antenna with electrical down tilt. My question is do you guys have any ideas or a source of literature that can point me in the right direction? Thanks.
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.
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4 hours ago, Usmc1968 said:
ERO glue, came right off.
I'll bet it did.
- Usmc1968, WRUU653 and TheLastBoyScout
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1 minute ago, WRXB215 said:
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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2 hours ago, Sshannon said:
Used to be able to go to Radio Shack.
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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3 minutes ago, Sshannon said:
HRO carries 300 ohm ladder line:
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.
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8 hours ago, SpeedSpeak2Me said:
Interesting... I'm glad someone else analyzed the N9TAX Labs antennas. I also have both the 2m/70cm and MRUS/GMRS versions, both with 16' of RG58U. For the MURS/GMRS (on GMRS) using a RigExpert Stick Pro, with the antennas hanging about 12' AGL (away from vegetation), I got slightly better results:
2m/70cm (UHF)
I also found that the Surecom SW-102's (mine is the "S" model)l are wildly inaccurate. I know they are popular, but the readings they give can be very misleading. As an example, it told me my Browning BR-6155 (fed with 50' of LMR400UF) has an SWR of 1.01:1 at 467.6000 MHz. My RigExpert Stick Pro, and my friend's AA-1400 both show 1.37:1 at that frequency.
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.
- SpeedSpeak2Me, WRXB215 and Sshannon
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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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27 minutes ago, WRKX466 said:
Can a Kenwood TK-3400 be programmed or cloned to uses GMRS channels , including repeaters?
Is it the ProTalk version?
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1 hour ago, back4more70 said:
GMRS (for emergencies) has an SWR of about 1.48.
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.
- WRXB215, WRYZ926 and back4more70
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37 minutes ago, CJK said:
Is there a way to program the Wouxun 935G to broadcast my call sign, in Morse code, at the end of transmission?
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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22 minutes ago, tweiss3 said:
Also, on an HT, you never really get an accurate measurement. Sure, it comes with the ground plane plate to attach, and it helps with the measurement, but you end up using adapters, etc. and it never shows accurately. Rotate or tilt the radio 10 degrees and the readings change.
BTW, on an HT, you shouldn't worry about SWR, if the antenna is the correct band split for your frequencies, just go with it.
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.
- Webslinger and Sshannon
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4 minutes ago, Sshannon said:
But simply being 50 ohms doesn’t make an antenna efficient. It just removes one cause of inefficiency in getting the signal to the antenna. You can have a perfect 1.0:1 SWR but have an antenna that just doesn’t radiate RF.
A 50 ohm dummy load will give you a perfect 1:1 match, but nothing radiates from it.
- Sshannon, Webslinger and WRUU653
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46 minutes ago, Sshannon said:
GMRS is subject to the restrictions listed for all the personal radio services. This is the rule that addresses scrambling:
95.381 Voice obscuring features.
A grant of equipment certification will not be issued for any transmitter type that incorporates one or more voice scrambling or other obscuring features for any of the Personal Radio Services that provide for voice (telephony) communications on shared channels (see § 95.359), if the application for such grant is filed on or after December 27, 2017.
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.
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1 hour ago, WRZT411 said:
I can kerchunk a couple of repeaters at sunrise and after sunset but not during regular daylight hours. Any thoughts on why? Thx in advance.
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1 hour ago, back4more70 said:
Which is why I carry One Radio to Rule Them All
Manufactured by Gollum Radios I'm guessing.
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1 minute ago, WRXB215 said:
Every day I become more and more convinced that is the most likely scenario we will face.
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.
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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1 hour ago, tweiss3 said:
I wonder if it could be radar, though that should stop at 450, but you know, the feds do whatever they want.
Also could be a 2nd image of 925.225MHz, but neither would exactly explain the issue around both locations.
Edit: 925 is part of the LTE band. ATT did just have that huge problem last week. It is possible that their outage included firmware updates for the cell tower equipment and now something is out of band/creating an image.
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.
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10 hours ago, WSAR863 said:
It has to either be very powerful (to penetrate canyons) or a satellite, right? My signal, on 18, appears to be coming from the direction of a cell tower, but I guess we'll find out. The one on channel 3 seems to come from everywhere, like your channel 18 signal.
What kind of radio is being used? If it's a cheap Chinese radio they're not known for good receivers.
Note that channel 3 is the Interstitial frequency, 462.6125, between the main channel 17, 462.6000, and main channel 18, 462.6250.
For GMRS the channel bandwidth is 25KHz so there is considerable overlap on channel 3 with the adjacent channels 17 and 18. If the radio doesn't have extremely good selectivity you're likely to experience significant bleed over on 17 and 18 from a strong signal on channel 3. Also a strong signal on either channel 17 or 18 will bleed over on channel 3.
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Here is one idea used on an expensive Motorola XPR7550 radio. Allows the use of an external antenna by using a stud type adapter to BNC. The ground is made externally using a strip of sticky back copper foil tape over the back side of the case to the chassis for the ground connection to the adapter.
Something like this could be use on the cheap radio.
https://youtu.be/O3KEazVQ-RA?si=UV8kiC5HQjQ3gqMG
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2 hours ago, WRYS709 said:
Or when I can get another one for $14,
At that price you can afford to destroy one or two and not feel too bad.
Changing Electrical Tilt On DB420-B
in Technical Discussion
Posted
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.