Too much antenna?

Status
Not open for further replies.

paulmohr

Member
Joined
Jul 12, 2017
Messages
171
Location
Adrian MI
Riddle me this Oh Great Antenna Guru's:

Is it possible to have an antenna that is too strong? I have three antennas for my scanner that I can use. And no, I am not using them all at the same time. I did a little reading on that theory and quickly learned it is a bad idea in most cases. So this is plugging one antenna in, then removing it and connecting a different one. Keep in mind I am not using any kind of fancy testing equipment. I don't have any, and probably wouldn't know how to use it if I did. I am just going by how far out I can catch a signal, how it sounds and the RSSI number in the ScanFree logging software.

First antenna is obviously the little rubber one that came with my 325P2 that is 6 inches long. It actually works a lot better then I thought it would. It has no problem picking up local 150, 450 and 800mhz. I live about 5 miles from most of the antennas in my local town, including the one for my county's trunked system. I can even get a fire department from about 15 miles away (156.105mhz). It is kind of scratchy and has a lot of hiss though. RSSI numbers are between 700-850.

Then I have a large TV antenna on a 30 foot tower. I don't know how old it is, it was here when we bought the house about 5 or 6 years ago. Judging from the elements that are on it it looks like it is made for FM, VHF and UHF. So before TV went to digital broadcasts. All the elements are still there and not mangled by the wind. It has a pre amp mounted right under the antenna. It also has a rotor that works. The control box doesn't look too old either. The tower is not all rusty and cable looks like it is in good condition. It seems to be professionally installed. RG59 cable though running into the house. It runs into an amplified two way splitter and the cabling in the house is all RG6. It is not a solid run though, there is one connector in the middle of what I would guess is a 15 foot run across the house. Then another connection to the 6 foot cable I made with the BNC connector to attach to my scanner. So 30 feet of RG59 into an amplifier, about 8 feet of RG6 to a simple F type connector, then another 8 feet or so to another connector and 6 feet of RG6 terminating with a BNC connector.

The tower antenna has RRSI numbers in the 1000-1100 range and managed to snag a 155mhz channel at over 50 miles away. It didn't sound real great though. It will not pick up the next closest trunking tower that is about 20 miles away, even if you point right at it. It is not real great with 450mhz signals either.

And lastly I have a home made OFCD antenna that is described on this site. 1/2" copper tubing, 48 inch top element, 18 inch lower with pvc connectors. If the numbers I just listed are wrong, it is my memory, I designed it to whatever the specs on this website were. It is attached to an unused chimney on the east side of the house (opposite side of the tower antenna). The T junction is 8 feet off the ground and the antenna is spaced about a foot away from the chimney about 21/2 feet from the side of the house. It is just strapped on temporarily for the moment so I could see how well it worked. If i keep using it I will raise it higher. IF I can get up the nerve to climb that high on the ladder lol. I am scared to death of heights. The cable is 25 feet of brand new RG6. Nothing fancy, just the white cable you can get at lowes with the pre installed terminals. That feeds into an amplifier with a single input and single output, not an amplified splitter. RCA 10 db 50-900mhz fixed gain. Then the 6 foot cable I made running into the scanner.

This set up has RSSI number in the 800-950 range. However, it seems to get more hits and is more consistent than the large tower antenna. Also some of the channels are more clear, no static or hiss like with the other two antennas. Some channels are, but not as many. Like the fire station in Blissfield about 15 miles away. The big antenna will get it, but it doesn't sound real great. The dipole seems to get it with more clarity and stays locked on better. This antenna can also get 150mhz signals from Detriot which is about 45 miles away. It actually picks them up better than the larger antenna. It however will not pick up the trunked system 20 miles away either, Just the local one here in town.

Someone in another thread explained to me that the 800mhz system are set up that way on purpose though so they don't spam other areas.

So if you guys were to take a guess, what do you thing is happening here. Is the large antenna too strong for local signals some how? Or are the RSSI numbers really useless data and the dipole is actually more efficient than the large antenna even though the numbers are slightly lower.

My current options are to either raise the dipole and attach it better, or climb the 30 foot tower and run all new cable.

Keep in mind all of the antennas work just fine for all my local stuff, but the dipole seems to be the best. But if I could pick up either of the next closest trunked systems it would open me up to a lot more of the State Police.

I fully understand that antenna's are pretty complicated and my comparisons are about as low tech as it gets. And that I am asking you to make wild guesses without the proper technical information. I am not asking for hard advice and I am not going to hold anyone to their best guess based on the crappy information I gave. Just your shot in the dark opinion on what might be happening. Don't think that if you all tell me to replace the cable on the 30 foot tower that I am going to run out tomorrow, go to lowes and buy cable, and them come home and climb that tower like a monkey. I can't really spend any more money on this for the next month or so and I am not going up that tower unless I can find a safe way to do it. Like some kind of harness or belt that I can attach along the way. I might brave 15 feet or so, but not 30 lol. By the time I got up there I would be shaking too much to actually do anything.

I am open to other options as well as long as they are not crazy expensive. Like mounting an antenna designed for what I am doing, or even paying someone to run new cable on the 30 foot one, depending on what they would charge. I have the tools to strip cable and attach compression fittings and have done that. I just don't like heights is all. And once we get to the 300 dollar mark I would probably opt to buy a second scanner before spending it on a slightly better antenna. Does that make sense? If it is a vastly better antenna that is another thing.

I suppose another option would be a second scanner and antenna specifically set up for 800mhz. That doesn't sound like a cheap venture or anything I could do real soon though.
 
Joined
May 1, 2017
Messages
95
Location
Basement Dweller, Huntley IL
You are currently trapped in the Scanner Antenna Black Hole in the cosmos. Save yourself. There is No Escape! It will only get much worse.

The best thing you did here was to explain it all. Fantastic job. You are chasing the antenna unicorn.

The TV antenna you have up there will never make a good scanner antenna, no matter what. It is on the wrong polarization. I have tried to use a large one in my attic on a 12 dB booster. It gave me way way too much signal, cell towers, tv broadcasts, pager intermods, and crap. Not really useable! The scanner comms are Vertically polarized, the rods would need to be Up/Down, TV signals use horizontal polarization. This still works fine for most local signals but not UHF or digital APCO P-25. The booster is compensating well for a big signal loss, but...give up on this idea. The TV antenna is best just used for TV off air reception only. The RG-59 yes, would also have to go. You could also try a cheap UHF only corner bay or bow tie bay type antenna in the attic, would work great for P-25 systems, but only fair/okay for the local VHF channels.

RG-59 coax has terrible specs for scanner buffs, just bad to use. Try to use RG-6 cable for everything. Here's a chart, cut the loss in half for 50' of cable. Don't fret the splice connectors, miniscule loss. But every 3 dB of loss is 1/2 of your RF signal lost. And every passive splitter port is another 3 dB of loss each port.

RG 59 Signal Loss (in dB) per 100 ft:

Loss at 50 MHz: 2.4 dB
Loss at 100 MHz: 3.4 dB
Loss at 400 MHz: 7.0 dB
Loss at 900 MHz: 11.1 dB
Loss at 1000 MHz: 12.0 dB

RG 6 Signal Loss (in dB) per 100 ft:

Loss at 50 MHz: 1.5 dB
Loss at 100 MHz: 2.0 dB
Loss at 400 MHz: 4.3 dB
Loss at 900 MHz: 6.8 dB
Loss at 1000 MHz: 7.0 dB

The best bet (and cheapest) is to use RG-6 with your OFCD and go up onto the tower if you can, as high as you feel like going up. And then use your TV booster on it. But you're really gonna have to have it properly grounded right. You may need to get it installed. But the best 800Mhz will come from a dedicated 800Mhz antenna, cut for 800 Mhz only. Build one, (yagi or j-pole or collinear if you're truly mad as I am) and run a separate cable from this antenna to your scanner. I put the Remtronix 800Mhz way up high in my attic, ran RG-6 feed from it to my scanners and it works better than you think. On most everything. You get really great 800Mhz plus good enough local VHF/UHF to use. But don't combine antennas on one cable.

You can have too much antenna, but for P-25 reception past 20 miles, off a certain tower system only, you're asking for a miracle. Too many factors involved. The RF power put out on 800 Mhz from the tower at 20 miles won't make it to you. It is designed Not To do this. It works like the Cellular towers. Check for some other useable control signal, check the site maps here for more tower sites. It may be that you won't be able to get that tower's talkgroups you want. You may get it to work 50% of the time if that, even with a perfect setup. The higher antenna is always best, but I've found that with P-25 digital, this Doesn't Matter one bit. 800Mhz signals propagate the same as your cell phone, it's the same band, how big is the antenna in your cell phone? I keep forgetting this myself.

With P-25 digital reception, nothing works like you want it to. Nothing will work perfect on any given day at any given time with any given antenna due to atmospherics, wind, rain, temps, humidity, foliage. Then there's LSM simulcast distortion to add in. With LSM simulcast distortion, if you are in a bad RF location-Nothing will work good at all. This is what it is, the Black Hole of P-25 Digital for us.

You won't get perfect APCO P-25 digital trunked system towers you specifically want unless you use a yagi pointed directly at the tower you want. And that antenna will yield poor reception for Everything else on VHF/UHF. The perfect solution is of course...a second scanner, dedicated to 800Mhz digital on a separate RG-6 fed 800Mhz cut antenna. Then a good ground to everything. This is a big issue. The very very best solution I have ever read is to... Disconnect Every Antenna Cable To Every Scanner You Own & get the cable Far Away from the Scanner, if Lightning is Anywhere within 100 Miles or You Will Regret It! Seriously. Put your Four separate RG-6 cable feeds in now, (you'll find a need) run them as desired for the multi antennas, plan where to put these antennas up, but also research good grounding principles.

One antenna will not work great with one scanner for everything. Put each separate P-25 site systems' tower freqs (one whole group) on a separate quick key. Don't combine many tower sites/control freqs together as it confuses the scanner's brains as to which control channel to sit on. Don't scan more than one P-25 digital system at the same time. Only scan a few VHF/UHF favorites at the same time with your P-25 digital system. Save up for the next 3+ scanners. Use the Great BCD325P2 you have now, just for the digital stuff. Buy an analog only VHF/UHF second/third scanner for the other (non digital stuff) off of Ebay or wait for a sale on Amazon. Ebay has deals on used analog scanners daily, as people dump these when their towns go digital. Even my 30 year old scanners for analog VHF/UHF receive just as good as the new digital ones. Tells you something.
 
Last edited:

paulears

Member
Joined
Oct 14, 2015
Messages
387
Location
Lowestoft - UK
RF-Guy's advice is on the mark. You've inherited and probably added to the complete mismatched mess. I'm intrigued where you got the RSSI information from, as it's widely used in wireless networking, but rarely in two way radio comms, where when people do measure signals, they measure at a specific frequency and produce a result in usually micro-Volts.The cable, the splitters, the years of moisture will all be impacting what comes down the line - and unless you are receiving TV, what the antennas appear to be designed for - anything else is juts a bit of metal in the sky. You also have another problem. Very often the radio bands are full of weak hardly receivable signals surrounded with mega strong signals. These strong signals can be filtered out, which then gives your radios space to work properly. Radio receiver design has conflicting requirements. It needs to be sensitive, have low noise and selective - able to reject frequencies it does not have an interest in. Expensive and well designed radio receivers can do this sooooooooo much better than and SDR, for example.

A really good antenna system can be too good, but just too good for a poor receiver. I live 700m from a high power data site, on 164MHz - two VERY strong outputs, and then our business radio allocation starts at 165MHz - putting up a better antenna for this band meant that the cheap Baofeng I often use for general listening had to be abandoned. The SDR on this antenna is hopeless - the two carriers that are ONLY on 164 appear at even spacing all over the place! The SDR is great for hearing what is there, but useless for NOT hearing what remains. There is also another technical problem - there is a maximum signal strength a receiver can handle - and if the signal goes over this level, you get distortion, with all the issues that creates - you can solve it with an attenuator, but that close really strong signal also causes the distortion - saturating the input circuitry - you don't know it's there, so you can't work out why performance on the signal you want to listen to is so bad.

That all out the way - you have what most people would love - a decent tower. With a rotator. If you want to listen to vertically polarised stuff, you could buy a log periodic design and put that on your tower. You could run a few decent feeder cables to a box on the tower and then try your other designs. Personally, I'm not sold on these off-centre designs on higher bands because you can usually get better gain and wider band performance from other types at VHF and above.

One piece of advice from my tower and ladder climbing days. Do NOT try the often suggest acclimatisation technique. The one where you go amp a few rungs to see how far your self preservation reflex is, then when you have calmed, do another rung and over and over again. It does work, but consistently produced somebody who has learned to reject the run reflex, and numerous times I've seen the big macho guys with a genuine fear beat it by sheer effort and willpower. This is not safe. The safe solution is to see if your fear is because of uncertainties with safety - so try a proper harness and attachment devices - work placement types so you can climb - and then WORK at the height you need to be. Many people climb, but are then unable to function properly. Can they let go with both hands and then use tools? My experience is that if you have to fight with willpower, you're best not to do it at all, and find somebody else who is comfy.
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
5,126
Location
Stockholm, Sweden
You should absolutly invest in a $10 variable attenuator with F connectors from ebay or amazon if you don't have a local tv/sat store. With that installed at your scanner you can dial in the perfect signal power without overloading your scanner.

As you have amplifiers at the antennas there is no worry about the cable types you have.
You should also invest in a FM trap filter to reduce the broadcast signals.

If you do not use that tv antenna for anything else you should have someone help you to tilt it on its side so it will be vertical polarized which will increase the signals from communication towers by 10-20dB and decrease the FM/TV broadcasting towers with the same figures.

There is no such thing as too much antenna if you have a variable attenuator to adjust the signal levels before it reaches the scanner.

/Ubbe
 

paulears

Member
Joined
Oct 14, 2015
Messages
387
Location
Lowestoft - UK
That 10-20dB often quoted only really applies to resonant antennas - the performance of a typical TV antenna on bands outside of it's design is very odd. One really key feature is the polar pattern - something sensible and useful in the design band - as in the polar patterns and front to back gain - get mangled. It normally looks like a forward facing ellipse with a few rear lobes - to the sides or the back. Shift away from the centre frequency and the ellipse shortens and the lobes grow larger, and increase in number. Once you've gone to a non-mathematically related distance from the centre, then the radiation pattern is a complete mess - no gain in particular in specific directions, and horizontal and vertical orientation making much less of a difference, as the lobes are not in one plane. If you look at antenna designs like discones - they are designed to have vertical polarisation, but as neither the top disc or the bottom cone are vertical, they are effective at a range of polarisations. A typical yagi, is not.

If that TV antenna is designed for 800MHz - it's pretty awful anywhere else. If the preamp is dsigned for TV bands, it too won't be that good at other bands - and good preamps have filtering in them too - another unwanted thing if you expect to use it for comms.
 

krokus

Member
Premium Subscriber
Joined
Jun 9, 2006
Messages
4,528
Location
Southeastern Michigan
With the distances you mentioned, I am guessing you are in Lenawee County. Which tower is the 2nd closest MPSCS tower you are trying to pick up? Is there another 800 MHz site between you and there? What about the ridge that runs western Washtenaw County?

Sent via Tapatalk
 

paulmohr

Member
Joined
Jul 12, 2017
Messages
171
Location
Adrian MI
Excellent, excellent, excellent information guys! Thank you so much. I was worried I put too much information out there and people would be upset or not want to read that much. I seem to have that problem. Short posts are not really my strong point lol.

The polarization issue had never occurred to me, I didn't even know that was a thing. I was trying to figure out why every one was saying a tv antenna would not work for a scanner when you look at the specs and they are designed for the same frequency ranges. I thought radio signals were radio signals, I had no idea they could be oriented differently lol.

And yes, I live in Lenawee county, between Adrian and Tecumseh, on the corner of Valley and 52. I "think" the two other closest towers to me are in Monroe to the east, and in Jackson to the west. Really my only reasoning for trying to grab another P25 tower is to expand my state police coverage. On the Adrian tower I can get post 14 from Monroe which gives me my local state police. And even if I could pick them up, I am not really sure it would even do what I want it to do. This trunking thing is a bit confusing to grasp. Like everyone is telling me, I don't get these signals because they are specifically designed NOT to reach me. If dedicated commercial grade radio equipment like the police use can't pick it up, why would I think I could with a 300 dollar scanner and a home made antenna, right.

The RSSI numbers I am getting are from the FeeScan programming software. It has a virtual control and logging feature. In the logging feature it shows the channel/ID, system, group, frequency and the RSSI signal. I have no idea if it is of any meaning or how accurate it is. I can also record if I want to, but I haven't messed with any of that yet. I do like the virtual control display though, it shows what is on the scanner screen and has all the buttons and stuff laid out so you can control it from a window. Which is nice when using a hand held.

Based on the information you guys gave me, and what I researched I will probably just move my dipole antenna up a bit higher and make sure it is grounded properly and just be happy with what I can get. At least for now, maybe later I will get another scanner and dedicated 800mhz antenna. At the moment the Adrian P25 site gives me access to Lenawee county agencies, Monroe city and county police and local State Police. And 150mhz channels I can easily pick up out to 30 miles away, and in some cases over 50. I have picked up Henry county in ohio, which is about 50 miles to the south of me, and I have picked up stations from the Detroit area which is 45-50 miles to the North of me.

I will look into the antenna tuner and maybe an SWR meter though. Even though I am not sure what they do or how to use them yet. I vaguely remember messing with that stuff in my CB days, but that was decades ago and I really don't remember much of it.

I would like to be able to pick up some more trunked sites around me, but it really isn't worth investing a thousand dollars and risking my life to do it. There are some things that frustrate me, but I can either live with the limitations or I will figure out what is happening eventually. Like for instance at 3 this morning there was a car chase that started in Michigan and the Lenawee sheriff was following them. They followed it all the way to Sylvania Ohio and then handed it off to local police and the Ohio Highway Patrol. At which point I lost the chase because I cannot pick up those trunked sites from my location.

There was also a large house fire on sandcreek highway right after that. I could follow the Blissfield fire department and all the other fire departments involved until they switch to Tac3, then I lost it. I have all the tac channels programmed in, and even tuned directly into the tac3 channel but never picked anything up after the switch. I also don't get any chatter from any of the township police and fire stations. Raisen, Adrian, Maddison, Palmyria ect. I don't know if they just don't use those channels, or for some reason I can't receive them. Raisen township department is literally right down the road from me. I checked the FCC database and the frequencies are correct. I have not verified the tac channels yet though, I will do that today.

All my questions and blabbering aside, I am actually quite happy with my purchase. It does what I wanted and more. It works better than I expected when I bought it. I originally wanted to hear my local police and fire, and the sheriff, and this does that and more. At this point I am just getting knitpicky and seeing what I can eek out of it. Just like I did with my little 50cc scooter. It was designed to do about 30 mile an hour. I looked at and said "what I can do to make this thing do 40 mph?". So I put an 80cc bore up kit in it, new cam, carb and tuned the drive train parts. Now it will do about 40 in under 10 seconds. But in the end it is still a cheap chinese scooter that I spend more time working on than actually riding lol.

I don't "need" this scanner for work or anything. I am not a reporter, photographer, ambulance chaser or super hero. It is purely for entertainment, and it works plenty well enough to keep me entertained. I am just some old man in basement listening to a world I don't feel like I belong to anymore.

Thank you all for your help, information and keeping me entertained. If it were not for this community and database this would be a nightmare. I could not imagine looking up all these channels and ID's and manually programming each one into my scanner.
 

paulmohr

Member
Joined
Jul 12, 2017
Messages
171
Location
Adrian MI
Ok Gentlemen, and I suppose a few women I re located my my homemade OFCD antenna. I moved it up to about to 15 feet off the ground on the same chimney. That is as high as my longest ladder would reach. I was going climb up on the roof and attach it at the peak which is a few fee higher. Problem was I couldn't make the transition from the ladder to the roof lol. Like I said I am a wuss when it comes to heights. I would have had to take both hands off the ladder to do it, and I just couldn't force myself to let go. It isn't death that scares me, I almost welcome it sometimes. It is ALMOST dying that scares me. Dead I am ok with, parallelized for the rest of my life scares the crap out of me.

So it is up there and clamped down pretty good. I made a home made wooden jig to go around the chimney and clamped it down with a really good wood clamp. I will look into one of those metal strap chimney mounts next month. I lucked out and found an unused cable from our satellite system that was coming out of the basement right where I needed it. Used to run to a spare room in the garage, it ended up never getting used. So I didn't have to drill any holes in the siding to get into the basement.

I connected the RG6 line from the antenna to one of those F connector couplers with a grounding wire port. Then I grounded it with heavy gauge wire I used to use for a high power trunk amp (8 gauge I think). I grounded it to the same block where all the cable, telephone and electric service uses. I just has a new phone line, cable/internet and new electrical service done last summer. So I am pretty that part is grounded to code and the block has extra ports to add things too. Turned out to be pretty handy.

Should I also run a separate ground wire from the actual antenna element to the main grounding system? Like clamp a wire to the bottom element and run it right down to the block? Or is the 75 ohm cable ground sufficient? Or should I get one of those grounding discharge units I have seen?

I need to shorten and clean up the cable inside, but it works for now. I had this bright idea of using a powered two way splitter. That way I could have a cable next to my computer, and another that would run over to my bed. I like to move it next to my bed at night. I cannot believe how much signal loss you get using a splitter, even an amplified one. The RSSI number went from high 900s to 550-600 after connecting the two lines. So I scrapped that idea and will just build a little longer line running from the amp to the scanner so it can reach different spots in my room.

I ended up trampling a few of my moms flowers because she put a flower bed in front of and around my entrance to the basement. I got attacked by a wasp and stung twice, scared a garden snake ( he should have eaten the wasp!) And I am a complete nervous wreck from climbing up and down that wobbly extension ladder. Nothing some Xanax and benadryl won't fix though.

If I want it done better in the future I think I will pay someone that knows what they are dong and is not afraid to do it. If I had one of those trucks with a bucket it would fine, but ladders I do not like.

After seeing the signal loss from that distribution amplifier I will definitely run separate cables if I get another scanner later. Almost all my work with running cable has been with TV, cable or small satellites. And the losses were not a huge impact on performance. Especially with digital television, cable and sat. As long as you have enough signal to make it work, it looks pretty amazing. Down side is if it drops out you lose everything, it doesn't just get fuzzy like the old tv systems. However it seems with radio signals a slight decrease in performance or signal loss really effects performance.

And I still need to look into the antenna tuner and swr meter. Thanks again for your help. I learned a ton from this thread alone. If I could Lindsey I would give you big ole hug for keeping this site up and running.
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
5,126
Location
Stockholm, Sweden
I wouldn't blindly go by the RSSI values. When using an amplifier it will amplify both the signal and the noise that could be a too much signal for the scanner. You'll want to have the highest difference of levels between the signal you receive and other noise sources. If you feed the scanner with a high level signal it will begin to compress the signal and loose the dynamic so that noise and signal levels becomes more equal resulting in a very bad reception even if the signal meter indicate full signal.

It's even more important with AM modulation to keep the signal levels within the receivers dynamic range. If you ever where to use a shortwave receiver you would soon discover that connecting a dipole or longwire antenna usually needs you to use the inbuilt attenuator to be able to hear anything and when using a loop antenna you would need to do the opposite and kick in all the preamplification you have.

So the correct use of antenna amplifiers and attenuators depend on the antenna and the signal strenghts in your area and of the background noise levels.

/Ubbe
 

krokus

Member
Premium Subscriber
Joined
Jun 9, 2006
Messages
4,528
Location
Southeastern Michigan
For which frequency range is the OCFD made?

Fire Tac 3 is 154.430 MHz. Unless you are within five miles of the scene, you are unlikely to hear any that traffic. (Even less so the handheld radios, which might only reach two miles. Especially if they are only transmitting one or two Watts.)

Sent via Tapatalk
 

paulmohr

Member
Joined
Jul 12, 2017
Messages
171
Location
Adrian MI
The OFCD is designed to whatever the specs are on this website, that is what I used to make it. I think its a 48 inch top element and an 18 inch lower element. I used 1/2 copper tubing and a pvc T fitting.

And yes, I am starting to learn the limitations of some radio waves. I am guessing with the Tac channels and 800mhz stuff they are intentionally using lower power or a certain frequency in order to limit range. Which makes sense for the intended users. One county on a trunked system doesn't need to spam the county next to it with information it doesn't need to monitor. And if you have 4 different fire departments show up to one scene they really only need enough power to communicate at that incident site. Everyone is probably within a quarter mile or less of each other so a lot of range is not needed.

Works great for them, kind of blows for us guys trying to listen in. But hey, it isn't my god given right to listen in on their transmissions so I guess I will take what I can get. I should really just be happy it is legal and the channels are not encrypted. I see a lot of the Toledo Ohio channels are encrypted, but it doesn't seem to be an issue in Michigan. At least not in my area. I don't even see any encrypted channels for Detriot.
 

krokus

Member
Premium Subscriber
Joined
Jun 9, 2006
Messages
4,528
Location
Southeastern Michigan
The OFCD is designed to whatever the specs are on this website, that is what I used to make it. I think its a 48 inch top element and an 18 inch lower element. I used 1/2 copper tubing and a pvc T fitting.
I have no idea which antenna design you are talking about. I am sure there are a few plans on here.

I am guessing with the Tac channels and 800mhz stuff they are intentionally using lower power or a certain frequency in order to limit range.
Higher frequencies have shorter ranges, due to atmospheric absorbtion. That is why 800 MHz frequencies work well for cellular and trunked systems. The trunked systems limit traffic on various sites, to not overload them. (For instance, radio traffic from Marquette is not carried on the Washtenaw MPSCS towers, and vice versa.)

Sent via Tapatalk
 

paulears

Member
Joined
Oct 14, 2015
Messages
387
Location
Lowestoft - UK
I suspect we may have confused you a little - An antenna designed for a specific band does not care what the signals carry - TV, comms, data, all are fine. Polarisation, however is vital. Regional TV broadcasting is horizontally polarised, while local broadcasting fro m those little relays, designed to cure dead spots, are usually vertical. Comms radio is almost universally vertical simply because the antennas on portable and vehicles are! Moving a radio 90 degrees produces no signal at all in many cases.

VSWR meters - these involve squirting power INTO an antenna a system and seeing how much comes back, hopefully none of the antenna is doing the job properly. TV antennas rarely have a decent VSWR - they're designed to receive, not transmit and they just optimise them for receive gain. An antenna analyser is a better tool for the job - it measures the VSWR at a range of frequencies and shows you what the performance is.
 
Status
Not open for further replies.
Top