marcspaz

I'm confused. GMRS is no where near 403. Its 462 and 467.

The Laird B4505C and it sub-models (BB4505CR and B4505CR) are non-tunable, pre-factory tuned antennas. If you recall from my Gain and SWR thread, I mentioned that some antennas are not designed to be tuned by the user. You need to read the product manuals for tuning instructions. In this case, you would have had to looked at relocating the antenna or checking for damage. Tuning isn't an option for you. Unfortunately, that antenna is likely toast. Even if you get a replacement whip, the chances of getting it within spec is almost zero. The whip being 0.5mm too high or too low could cause issues. I would recommend buying another antenna.

@Lscott... There is a Hobby lobby near my house that was/is using MURS channels. I can hear them at my house, 11+ miles away. No way are they running legit power or equipment. Many businesses are doing the same thing on the FRS/GMRS frequencies around me, too. It's mind-blowing that the mall has an ERP of 70 watts. What on earth could they need that kind of power for? Around here, I can talk 10+ miles, full quiet with 2 watts on a 50' mast.

I have a set of Motorola radios I use with the family, and occasionally for outdoor stuff. I drive around with them on once in awhile too. I hear people (mostly businesses) using them pretty regularly.

Yep.. I used to go to Thompson Raceway Park every year for a drag race called the Buckeye Brawl. Takes about 5.5-6.5 hours to get there depending on traffic and weather. Nothing like driving a 10" pro-street race car 800 miles round trip.

I'm a computer scientist and communications engineer. That last thing I want to do is more digital when I'm out of work. I have a WinLink account that I have never used. No FT8, no FLDIGI, no DMR. I love warm analog static. LoL Besides, face to face to enjoy company... not to talk shop. Familiar subjects just helps get the convos started.

I forgot to post these after I took the picture. Keep in mind, for the sake of this topic... this is not very portable @ 67lbs. http://fiveguysracing.com/marc/HAM-GMRS/20200723_190831.jpg http://fiveguysracing.com/marc/HAM-GMRS/20200723_190844.jpg

Fantastic. I appreciate the lead. I will check them out.

I just checked them out.. wow, their warranty is great. 11 years on the 100 ah deep cycle. But its almost $1,000. I may go this route if the solar system I have will charge it... but I'll be crying the whole time. LoL

This is great advice. I would love to get an LFP and it may be next battery. My system primarily runs off of the solar panels and the battery is there to handle heavy draw spikes when I need to use the amp. I think I need a different solar system to switch to LFP.

Duracell. I'll share a picture tonight.

25-35 ah battery will give you hours of 50w use. If you go 5w or 15w, you can use a smaller 10-15 ah battery and still run for several hours. I have a 100 ah SLA AGP battery that I can run a 100w radio for 11-12 hours at 50% duty cycle. My battery weighs almost 70lbs, so unless you need it, I wouldn't go that large at all.

There are a couple of techniques. I personally tune for the center frequency of the band I plan on using. To be sure you are centered, you check the highest frequency you will use and the lowest frequency you will use. If the SWR is the same on both, you are good. If the SWR on the high frequency is higher than on the low frequency, your antenna is too long. If the SWR on the low frequency is higher than on the high frequency, your antenna is too short. The biggest problems you will run into with GMRS antenna tuning is, unless you have an antenna analyzer, that method is tough to use since you can't tune to the center frequency. Also, in centimeter radio, if you trim the antenna as little as 1 millimeter, you can drastically change the SWR. So, its a slow process and easy to mess up an antenna.

Adding to what was posted above, you do not need to have the tone programed to the simplex channel in order for the repeater channel to work correctly. They are completely separate.

I wish we all lived closer. I would love to sit down and chat with many of you. There is a lot of knowledge and experience in this group. I would definitely bring some doughnuts.

That is the most politely anyone has ever told me that I'm full of crap. LOL

If I make a mistake, please let me know. I do this stuff all day as a professional and sometimes the brain gets fried. Especially at 12:00 AM.

You are correct an I will correct it. Gain factor of an isotropic antenna is 1.0, not one BD... typed a lot. type-os happen. You guys are killing me, though. I specifically said I didn't want to science it up so I didn't confuse people. SMH Explain stuff like a little kid is reading it so people who have no idea what is being discussed can at least comprehend the general concept. All that stuff you guys posted is wasted on me. I already know it. The target audience is not going to have a clue what you wrote means. EDIT: That's not true... what I described about the radiation pattern and its general shape as gain increases is correct. I buggered a type-o. That doesn't make the rest explanation of incorrect.

That stinks... I have been making cables for 35 years. Always do them by hand with a straight razor. Make sure its sharp so you need minimal pressure and you will never cut the shield or center lead by mistake. The only time I use a tool is when I strip very thin cables that I can hold with needle nose pliers and wire strippers like the one in the picture. And I don't bother setting the guide stop. Again, just make sure they are sharp and use light pressure to squeeze and twist and you are good to go.

Good point. I dont have an NMO mount on my vehicles and I don't have a UHF 1/4 wave antenna. Otherwise I would redo the test to see the difference. That would be another point of consideration for antenna tuning as well.

Actually, its a type-A to so239. Some of the wavering could have been from the cheap cable and mag mounted. My analyzer doesn't read cable impedance or capacitance on UHV, so we can't see what's happening on that side of things.

That is kind of surprising. The Wilson antennas are typically really good. Any chance you have access to a 108" whip to test with? It may be worth it, if you can borrow one I went from a Firestick to a Wilson 1000 and jumped from 2-3 miles to about 8.5 miles. When I switched to a 114" whip, my range jumped to 18-20 miles reliably... 26 miles on the ragged edge and the occasional 40+ mile contact, depending on my elevation and the other station.

Are you using a Firestick?

This is the other video... hopefully this will help. https://www.youtube.com/watch?v=P5GiPLzVzbg

Hey folks... I have been seeing a lot of antenna related posts lately. Some info I have read lead me to create this post. I want to try to help people understand design types and how antenna SWR and Gain are impacted. I am not going to get too technical, because I don't want new people to feel lost or leave with more questions than answers. As an FYI, while the concepts apply to all antenna types, I will be focusing on vertical antennas, such as what we use on our vehicles. First, lets discuss basic antenna standards and why antenna length matters. The best way to describe how basic antenna length is relevant, is by comparing an antenna to a speaker. Pretty much everyone understands that a speaker vibrates to make noise. We also understand that small speakers do a better job at making very high frequency sounds (tweeters) and really big speakers are better for making very low frequency sounds (like a sub-woofer). Antennas are the same way. The lower in frequency, the bigger (or longer) the antenna. The reason for this is because, like a speaker, antennas resonate (or vibrate) the best at one very specific frequency. As you go higher or lower in frequency, you are moving away from the antennas resonant frequency This becomes important for several reasons. One is because the closer the antenna's resonate frequency is to the frequency you want to transmit on or receive on, the more range and fidelity you get. Another reason is because the energy that gets sent to the antenna must go somewhere. If the antenna is not at the correct length to vibrate at the desired frequency, that energy gets wasted by being "reflected" back into transmitters, as well as desensitizing receivers. Any energy that gets reflected back into the radio is typically identified by the Standing Wave Ratio (SWR) or the ratio of transmitted (forward) energy vs. reflected (reverse) energy. Here is why we watch SWR. If your transmitter is putting out 50 watts, and your meter says you have an SWR of 1.7:1, that means only 45 watts of energy leaves the antenna and 5 watts goes back into the transmitter. A high SWR not only causes power loss, but it also generates heat as well as applying reverse electrical energy to the parts. If enough of a percentage gets reflected back into the transmitter, it breaks. It is very well documented that with the current technology we have, the threshold is an SWR of about 3.0:1. So, now that we understand, on a very basic level, why antennas need to be a specific length to work the best, and also have a basic understanding of what SWR is, lets discuss antenna design. So, what's the standard? An isotropic antenna. This is a theoretical antenna that radiates equally in all directions with the same intensity. Basically, a perfect sphere. The antenna is said to have a power gain of 1 in the spherical space all around it and has an efficiency of 100%. The concept of an isotropic antenna is often used as a reference antenna for the antenna gain. What is antenna gain? Glad you asked! There is a lot of science behind that... so I am not going to bore you with science. Instead, lets talk about food! Everyone loves food and its pretty easy to understand. So, the concept of gain is this... you only have 100% of your energy available. There is no such thing as an antenna magically giving you more power. You know the perfect sphere radiation pattern mentioned earlier... well in the real world, the closet we have ever come to creating that, actually looks more like a doughnut. Imagine a perfect doughnut. Sounds yummy right? Well, you only have 100% of the doughnut. What do you do if you want the doughnut to be wider, say... to fill a box better from side to side? I mean, its a whole doughnut. Easy... you squish it from the top and bottom. Then the doughnut gets shorter from top to bottom, but the food has to go somewhere. So, it spreads out wider or "gains" width in sacrifice of height. Well the more you squeeze from the top and bottom, the wider it gets, but loses height until the doughnut is perfectly flat and the 100% of the doughnut as been spread as far as possible. The squished doughnut thing makes sense, right? Antennas that have "gain" do the same thing. They squish the radio energy doughnut, forcing it to be wider to cover more distance, but at the sacrifice of signal height. This means that while you can transmit and receive further side to side, you lose elevation. Lets imagine you are at the bottom of a hill and your buddy is at the top. If you don't squish the doughnut, he can hear you because the doughnut is at its full height. But if you squish the doughnut, people further away at your level will now hear you, but your buddy who is very close at the top of the hill will not. So, gain has a trade-off. If you live in a hilly or mountainous area, you may want to avoid high gain antennas, so as your elevation changes, you are less likely to lose touch with someone. Compare that to being on the water, in flat(ish) desert or talking aircraft to aircraft, you may want a very high gain antenna, because there will be no significant elevation differences. Now, from here, we could talk about the benefits of stacked phase element antennas, takeoff angles and a bunch of other stuff. However, unless you have a more advanced understanding of antenna propagation and design, and plan on getting into some high-tech stuff, it will likely cause more confusion. Not to mention, for what we are doing... those items are almost not relevant when it comes to helping you pick the correct antenna for your application. So, let talk about how gain and SWR can really be confusing and how numbers can trick you into making a mistake. Remember when we discussed antennas needing to be a specific length to resonate at the desired frequency? Well, many high gain designs cause the antenna to properly resonate at only small segments of the frequency spectrum. Basically, what these means is (as an example) instead of being resonant and having good SWR across 100 megahertz, the antenna design may cause the antenna to only be resonant and have proper SWR at 10 small groups of frequencies inside that same 100 megahertz range. Watch the two videos linked below for a better understanding. In the first video, I have a Diamond NR7900A mobile antenna. It has 3.7db gain on VHF in the 140MHz-160MHz range, and 6.4db gain on UHF in the range of about 440MHz-500MHz. You will see that while measuring the SWR (or the antenna and cable resonance) you will see that in the VHF segment, the SWR varies somewhat quickly, but only has a single swing, from high to low and back to high inside of about 20MHz. When I switch to UHF and test the higher gain portion of the antenna, you will see the the SWR bounce up and down a few times as I sweep about 30MHz. This shows that the higher the gain, the more the antenna design may actually make it so the antenna is not usable on your desired frequency. Of course this all varies by brand and model, but the principle is still universally true. https://www.youtube.com/watch?v=Rh6w46VM_Ng Now, in this second video, we are looking at a UHF 1/4 wave antenna. This antenna is considered to have a gain factor of 1, and any number times 1 equals itself... so effectively, no gain. You can see that we sweep over 50MHz and while the SWR wavers a little, the SWR is stable compared to the high gain antenna and 100% safely usable through the whole spectrum, never going over 1.4:1 from 440MHz to 470MHz. Again, reinforcing the idea that the closer the antenna is to the desired resonant frequency and the less you squish the doughnut, the broader the usable frequency range will be, the broader the geographical coverage will be, the less risk of losing power due to poor SWR, and less risk of damaging your transmitter. https://www.youtube.com/watch?v=P5GiPLzVzbg So, to wrap this up, I want to discuss antenna tuning. Some antennas may need to be cut to the proper length to resonate on the desired frequencies. This is typically done with antennas that either have no loading coils (1/4, 5/8, 1/2, 7/8 wave length antennas for example) as well as some bottom loaded antennas. A bottom loaded antenna is an antenna that has a whip that is not the correct physical length to be resonant on a desired frequency, but the coil of wire on the bottom makes the antenna electrically the correct length. General speaking, for VHF and UHF, I recommend staying away from antennas with coils in them if they have been physically shortened for looks/clearance reasons. These antenna work, but are not very good performers. That said, there are some antennas that are "pre-tuned" at the factory to perform correctly in the indicated frequency range. These are typically gain antennas that have a collection of coils and capacitors on the antenna to help create the phasing and properly stack the elements. These are referred to as LC networked antennas. If you have an antenna that has stacked phasing and/or LC networks and you can't get a good SWR... unless the manufacturer provides directions on how to properly do so, do NOT trim the antenna to try to achieve the proper resonance, as you will only damage the antenna. The coils, capacitors and whip elements are precisely cut to work together. If you do not get a good SWR, either you need to pick a new location to install the antenna, the antenna is not properly grounded or the antenna is damage and should be replaced. If you do trim a stacked phasing and/or LC network antenna, in most occasions, the antenna never gets to the proper length regardless of how much you cut the whip and you end up tossing the antenna in the trash. If you get it tuned to a target frequency, it's usable bandwidth will be so small that the antenna will not have any real value. I have seen some people try to tune high-gain antennas, get them tuned to about 1.7:1 or even 1.9:1 and as soon as they tune 10KHz in one direction or another the SWR skyrockets. I hope this helps with some of the antenna questions.