marcspaz

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.

This will give you an idea about typical usable bandwidth of a stacked phase dual-band VHF/UHF antennas. I will shoot another video with a single band 5/8 wave a little later, so you can see the differences. This is a Diamond NR7900A 2m/70cm. https://www.diamondantenna.net/nr7900a.html https://youtu.be/Rh6w46VM_Ng

Comet CA-2x4SR dual-band antenna has a capacitance hat to tune it for GMRS simplex frequencies. It works really well on the FRS and repeater frequencies too. I have tried a dozen or more antennas. For high gain and solid range, it can't be beat, in my opinion. 6.2 db gain, 40" tall so it works with a mag mount, and rated for 150 watts if you want to use it for other UHF and VHF applications.

Honestly... 6 miles is not good, at all. You have a massive elevation advantage going everywhere but south. And you should still be able to get 6-8 miles south while barefoot. There is only about 400 feet of elevation difference going 20+ miles in every direction but south. Unless there is something I'm missing, 12.5w SSB, you should be able to talk north almost all the way to the shore line... out to Buffalo to the west and at least 20 miles or more to the east.

There is a guy I know that puts "swing kits" in radios and you are right.. the SSB never works when he is done. But... I thought OP said it was turned down to 2.5 wattsto drive the amp. I have to re-read it. I'll tell you this, anyone running a de-tuned radio to accommodate their amp, likely has a home made amp done by guys who think/claim they are experts, but have no idea how to build a filter or ALC circuit. You open the box and there are heat syncs, a few Toshiba PAs and the few parts needed to make the PAs work... and that's it. Best part of the post. I LoL.

Hmm nice performing radio, but I'm not sure if the AM and SSB power are separate. I would gi e the shop a call and ask if SSB is still at the factory settings... assuming you don't feel like spending money on a meter for a one-time use.

Are you running a modded galaxy? Those are fantastic and have a lot of potential. If so, the AM and SSB power are adjusted separately, so the SSB side should still be at 12.5w. The DX 44 HP goes to 40w bone stock and some models go to 100w. The export guys have it made with their CBs. The FCC should just let US operators use amps, since there are no emergency services down there anymore.

The MFJ-1702C could be more of a problem than anything. It has a center-off position that sends the connections to ground, for lightning protection. Forget to turn that switch all the way to one side or another just once and your radio is toast.

I guess that all goes back to the layman's definition of integrity being, doing the right thing, even when no one is looking. As gentlemen and ladies, we all agreed to play by the rules. That's a huge plus I see to communities like ours. Most of us are here because we want to do the right thing. Many of us have been down the other path and don't like were it leads.

I agree with BoxCar... when operating on FRS frequencies, with an FRS compliant radio, you adhere to FRS rules... no ID required. The only problem I see is, the radio is not certified for FRS use, nor can it be due to the removable antenna. So, by the legal letter of the law, you are using GMRS hardware (not FRS compliant hardware) therefore you are using GMRS privileges. You need to adhere to the requirements for GMRS use, not FRS. On the flipside of that, I would never advocate that you flat-out break the law... but the FCC doesn't walk around inspecting radios while people are doing whatever they are doing. In fact, I filed several complaints with the FCC in the past few years, about grossly illegal activity on amateur radio frequency, handing them all of the evidence and proof of who was doing it and the FCC basically ignored everything I sent. They sent me an email saying they would look into it, and nothing happened.

Here's the thing, for some of us, its entertainment or emergency communications. However, my family use our radios around the house while working in the yard, while racing my car to talk to my corner spotters and crew from the track, while fishing, 4wheeling, hiking, spending time at the park, caravaning somewhere with multiple vehicles, and on and on. The list of things in our lives that we can integrate radio for the better is endless. Therefore the "image" to draw people in are endless. The best way to advertise isn't with someone specific to radio or activities you can improve with radio, but rather, find a common image that will have the most amount of impact on the heartstrings of your target demographic. The radio really has nothing to do with it. People buy toys and non-essential products based on emotions, using how they feel to justify spending the time, money and effort. That is... if that's really what the end goal is. If you're trying to sell radios, learn your target demographic. Asking folks like us is going to be a mixed bag of tricks that's just going to cloud that even more.

Awesome! Congratulations! You are going to love it. I talk to people around the planet, daily. The entertainment never gets old.

For me, it was a collection of conditions. My family spends a significant amount of time in rural and undeveloped areas with no cellular infrastructure. Being able to have some form of communication while on foot or mobile, without everyone getting an amateur radio license, was a must. Especially when we tend to move about in separate groups. Also, somewhat in the same category, I do things like 4-wheeling and other outdoor activities. Many of my friends use FRS and GMRS to communicate while spending time outside. It seems to be going more mainstream. Then, of course, there is always a risk of infrastructure failure. I needed a way for my wife to reach me while I am out of the house, if an emergency occurs. She had her amateur radio license, but it long expired and she is not interested in getting it again. There are several public GMRS repeaters around me that run on emergency power, if needed. So, it was just an obvious and affordable option for our needs.

Yes.

Yes that is normal. Tone is tone encoding to open the squelch on the repeater, but it doesn't require you to receive a tone to open your squelch, which means you can hear everyone on that frequency. TSQL is tone encoding to open the squelch on the repeater AND your radio. So you will only hear station that have the proper tone encoding. The only way both fields will allow a value is if you use cross, which allows for split tones.

I am onboard with this. For Field Day, I was only 100 feet away from my co-operator, but we used HT's so we didn't have to yell between the two tents. This is how close we were, but the HT's made life a lot better.

I haven't. I have 3 radios in my Jeep right now. 4 on days I need the mobile repeater.

Sure... I have some saved on my PC. When I get home, I'll share a couple. I know Hackaday provides direction finding with a bunch of online SDR's. I don't remember the others. Edit- I just remembered... WebSDR has a whole list of services. Just pick a station that covers the frequency you want to use and be sure direction finding is one of the services.

What I wrote is all required by law to put up an antenna tower. It doesn't matter who owns it or what service/band its on. Even if someone puts up a Rohn 45 in their backyard, all of the things I wrote are required by law and FCC rules. If private owners choose not to, they are in violation of federal law. If someone has a private use repeater at their house or business and its mounted on a building not more than 10' high from from top of the roof, then I suppose it would not go through any of that... but it wouldn't be much of a repeater, either. I guess it would be okay for their HT's while around the house/neighborhood, but that would be about it. As far as finding a station (and owner) that does ID, that is actually really easy. There are free, online RF detection centers all over the globe. Especially here in the US. Once you have the address, you can lookup the land owner and you're done. I have a local UHF broadband repeater that started causing issues around here. I was able to find the repeater in just about 15/20 minutes. It happened to be owned by the local FD, so it was easy to find out who to talk to.

Depend on power levels, what bands you are setting up for and if you plan on using them both at the same time. If only one will be on at a time, as long as the antennas are not a wavelength apart (of either band) or wave length segment apart (1/4, 1/2, 5/8, etc.), then there should be no noticeable impact. That said, the further apart you can get them, the better off you will be.

No, but the Army and Air Force have been asking me to join every few months for years. I keep turning them down because I could be deployed outside the US. MARS doesn't pay, so I need to keep working while serving. I can do my regular job remotely while on a deployment (during down time) domestically, but I can't VPN in if I am overseas unless I get special hardware. My main served agency will only give me that hardware if they are the ones deploying me. So, no MARS or CAP service until I retire.

Repeater sites are (or at least should be) registered with the FCC. In order to put up a tower, there has to be permits issued, an environmental impact evaluation, an FAA Risk/Impact evaluation and a RF exposure evaluation, determining RF exposure health risk to people/animals in the area... and all submitted to the FCC as proof that you are in compliance with all applicable laws. Plus the FCC regularly does site inspections. These systems don't cover a tremendous amount of real-estate and there are not many of them in many areas. If a machine starts doing something stupid or is non-compliant, I promise you, unless the owner has completely ignored every single law and requirement, they know who owns what machine and where to find both the machine and its owner.

Per 47 C.F.R, Part 95 Subpart E, §95.1751 ( c ) states that the repeater doesn't need to ID itself if... (2) The GMRS stations whose communications are retransmitted are properly identified in accordance with this section. So, even if the license holder is not using the machine, if people that are using it properly ID, the the repeater is considered in compliance with ID requirements.