Anybody here use a CB, FM or HAM radio?

reply to post by TheRedneck


Again, if you use the CB antenna close to it’s designed operating frequency, there will be no mismatch. Ham and CB antennas are designed for the same impedance range. 30 to 75 ohm (50 ohm nom) The 10 meter band is close to a CB antenna’s designed operating frequency. The ham transmitter set to 10M will usually see close enough to 50 ohms that it will be perfectly happy. You may have to tweak the tuning on the antenna to get the SWR to the lowest possible, but that will be all.

The only problem you can possibly have to deal with is reduced power handling capability of some mobile/cheap base antennas. But there will still be no impedance mismatch.

Saying that there will be a mismatch is just technically wrong, no mater how simplified it is.

…….edit………
Now saying that a CB antenna can’t be used on all of the ham bands would be correct. But connecting a CB antenna to a ham transceiver does not automatically cause a mismatch. Using an antenna on the wrong band causes the mismatch. And that will go for any antenna, not just CB antennas.

reply to post by Mr Tranny

Again, if you use the CB antenna close to it’s designed operating frequency, there will be no mismatch.

Wrong. There will be a mismatch. There is a mismatch on every CB antenna depending on the frequency one transmits on; CB frequencies are contained in a narrow (440 KHz) band and thus a match on the center frequencies will minimize the match on the extremes to an acceptable level. Proper tuning of a CB antenna in this manner is necessary to protect the radio.

Some antennas come from the factory described as "pre-tuned," but they are typically the ones that don't transmit or receive very well because the design to allow a wider bandwidth at low impedance mismatch also sacrifices quality of signal.

Ham and CB antennas are designed for the same impedance range.

CB antennas are designed for CB frequencies, which range from 26.965 MHz to 27.405 MHz. The impedance must be matched to that range of frequencies, and the most common method is to tune the antenna to match channel 19 at 27.185 MHz, approximately the midpoint of the band.

Ham frequencies are allowed over a wide range of frequencies, one of which is the 10-meter band. A CB antenna may be retuned to work on this band (since the 11 meter wavelength CB band is larger than the 10 meter ham wavelength), and some antennas are specifically designed to cover both bands (see the comment on "pre-tuned" antennas above), but that does NOT mean that one can just hook a 10 meter ham unit to a CB antenna with no worries. One cannot hook a CB to a CB antenna with no worries unless the SWR is set properly.

It is entirely possible you have a dual-band antenna, or that you got real lucky and your CB antenna happened by chance to be far enough out of tune to match the ham frequency. But that does not mean it will work for the next guy. Antenna impedance is a function of wavelength, and a mismatch between the impedance at the operating frequency and the driving signal can cause an overload and burn out outputs. It has been happening to people since the radios were introduced, and so far as I know no one has suspended the laws of physics.

TheRedneck

reply to post by Gazrok


www.broadcastify.com... this is interesting...

www.broadcastify.com...

reply to post by jtma508
well a 1.5kw liner is not that much of a drain on power, 6 6kd6 will get you that on 12v dc, ran one with a golden eagle base on a 12vdc converter for 12 hours a day www.ebay.com... to show the kind i had gave it up to mush BS on the old 24ch www.ebay.com... ec6b2990a yea it was back then now a corba 148 GTL will do www.sonicelectronix.com... h_google_pla&scid=scplp3613384&gclid=CObSsbqw8rgCFSJlMgod_n0Ayg call sign KMBK 5219 UT am HELL RISER

reply to post by Mr Tranny
you are right to a point cb is 50 ohm, ham 75 or up this can be over driven 50 ohm to 75 ohm by base loading, you can get a cb anti to run ham feq or you can by ham and cb combo antenna www.ebay.com... cb/ ham in one antenna there are others out there run duels for best out put and reception moon raker 6 is best for base unit. There are home made ones 1/4 wave to 1 full wave but then this is if you have the time or the practice and the money to fix rebuild what you will burn up trying to get or going for CQ-CQ- CQ- DX, that's long distance conversation that says you up and running can you hear me now.

In the 70,s cb here went crazy with nearly every channel was busy. I had a Midland, then a Lafyayette and ended up with a Cobra 148GT with a 30 foot arial sticking out the roof of my house.
In the car I used a 40 watt burner and loved driving past the local TV shop when all the tvs would go crazy when I keyed the mic.
I used to talk to people in the USA and also in Germany and all over the world using the side band channels. We would send each other little cards and presents to confirm we had talked.
I had a fire stick fitted in the car and we just loved it.
Sadly it's no more but was good while it lasted.
We had them in our trucks and used them all the time.
Happy days.......

Any transmitter is designed to tolerate and “impedance range” That is because even an antenna that is cut exactly for the frequency you are on, will present an SWR up to 1.5 to 1. A dipole is a dipole. Given similar radiator diameter. Just because it’s cut for 27 instead of 28.5 mhz does not mean It’s SWR will increase appreciably quicker when you get 1mhz off cut frequency. When you operate a dipole cut for the CB frequency on 10, or vice versa, you will get an SWR that is usually under 2 to 1 which is pretty much the accepted SWR limit for the operating range of an antenna for most transmitters .

Loaded antennas usually have a narrower SWR bandwidth, but those antennas can usually be adjusted to the band in question to the point that they are perfectly usable on the 10m band.

Funny how someone that says they don’t even have a license to operate on those frequencies is telling me that what I see in real life isn’t true. But heck with that, 20 plus years of using antennas, building antennas, and actual operation on those frequencies.be damn. Everyone here can believe what they want.
All i say is...Have fun.

BTW…bekod, CB and ham transmitters are generally designed use 50 ohm nominal transmission line. TV is the one that uses 75 ohm transmission line. Depending on the antenna design, sometimes using a 75 ohm line will yield better results, But that applies to CB and ham antennas. It is generally within the acceptable impedance range that most transmitters are designed to operate into.

reply to post by Mr Tranny

Funny how someone that says they don’t even have a license to operate on those frequencies is telling me that what I see in real life isn’t true. But heck with that, 20 plus years of using antennas, building antennas, and actual operation on those frequencies.be damn. Everyone here can believe what they want

No, I never took the test because I didn't have time to... I was too busy designing and building electronic devices.

You have an operator's license, which is inclusive of some technical information, and 20 years of practical application. I hold a degree in Electrical Engineering and 30 years of design experience. You use the radios; I can make them.

An antenna's impedance is matched to a transmitter when the SWR is at 1:1. Period. That happens at one and only one frequency . The farther from that frequency one varies, the worse the impedance match. As long as one stays below 1:1.5 (or even 1:2 for very short periods and low power levels), there should be no problem, as radios are built to handle a certain amount of mismatch. But any amount of mismatch of impedance will affect the transmission efficiency to some degree. Too much mismatch and the antenna becomes a short to the transmission circuitry and causes too much current to flow, overheating and potentially destroying the output transistors.

I'm not trying to convince you, sir, as you already know more about this than anyone else; I am, however, trying to keep others who do not have omnipotent knowledge from destroying their equipment over bad advice.

TheRedneck

reply to post by Gazrok

I have one in the truck, but haven't ever really used it.

I don't know about anymore, but long haul truckers used to converse with each other on the road about weather, road conditions, "Smokeys" (highway patrol), etc. On a long trip you could always tune into the local truckers on their radios and ask them about good places to eat or best roads to travel. They were helpful friendly back then and helped pass the time. The radio in your truck is a good asset if you get stuck or need directions. Is channel 9 still reserved for emergency use only?

If the power in your neighborhood is out, you can always turn on the truck radio to receive emergency news and get updates. Amateur radio clubs would take it upon themselves in an "emergency" to inform the world by radio. I'm sure CB wouldn't be overlooked.

Edit to add: You could try parking on a mountain top overlooking town and transmitting to see how far it reaches. Line of sight works better for CB. A signal strength meter on the front of your radio (if it has one) will tell you how strong the signal is you are receiving. You can ask anyone responding their location and what signal strength they are receiving from you. That will give you an idea your antenna is hooked up and working properly.

10-4 good buddy.

Originally posted by TheRedneck
No, I never took the test because I didn't have time to... I was too busy designing and building electronic devices.

You have an operator's license, which is inclusive of some technical information, and 20 years of practical application. I hold a degree in Electrical Engineering and 30 years of design experience. You use the radios; I can make them.

I have had plenty of experience inside the equipment. I have over 3000 tubes in my personal stockpile. Ranging from kw level metal ceramic power tubes to submini tubes used in military radio equipment. Countless thousands of transistors, ic and other componets. I will not even get started into what I built and repaired over the years, because this is starting to sound too much like a pissing contest

Originally posted by TheRedneck

An antenna's impedance is matched to a transmitter when the SWR is at 1:1. Period. That happens at one and only one frequency . The farther from that frequency one varies, the worse the impedance match. As long as one stays below 1:1.5 (or even 1:2 for very short periods and low power levels), there should be no problem, as radios are built to handle a certain amount of mismatch. But any amount of mismatch of impedance will affect the transmission efficiency to some degree. Too much mismatch and the antenna becomes a short to the transmission circuitry and causes too much current to flow, overheating and potentially destroying the output transistors.

If you look at the specs of most transmitter equipment, you will find that almost all business and ham transmitters are designed to operate at a 2 to 1 SWR at full power, at nominal duty cycle. That is a resistance from 25 to 100 ohms. Outside the 2 to 1 SWR range, then they will start folding the power back to protect the circuitry because it is outside it’s full power operational design range.

That full rated swr bandwidth is what determines the operation range of an antenna/transmitter combination.

That is why it’s called 50ohms “nominal”. Not “average” or “normal” The equipment is designed to drive a load that is within a specified range. “A nominal range” That range is 50 ohm +/- an allowance. Because in the real world, the impedance the equipment sees is almost never truly 50 ohms. It will almost always be a compound resistance consisting of real resistance and inductive resistance. AKA reactance

To call an antenna/transmitter system “mismatched” when the transmitter is operating within it’s nominal full power rated specifications when it is driving that antenna, is a bit much.
..........edit.............
And just for clarification, for those that don’t know. 2 to 1 SWR represents about 11 percent reflected power. If you hook a 100 watt transmitter to an antenna with 2 to 1 swr. You will have 89 watts transmitted, and 11 watts reflected back to the transmitter.

It was a nice day to be outside so I decided to do a little antenna experimentation. Because the only thing that counts is real world results.

WYSIWYG.

An elevated ground plane with sloped radials to achieve as close to a 50 ohm resonance as possible. Constructed out of thin 22 gauge wire to make the bandwidth as narrow as you will ever see on a real world elevated ground plane antenna.(smaller diameter the radiator elements, the narrower the SWR bandwidth)

(And I did not cut/stagger the radials and vertical radiator to widen out the usable bandwidth. This is a straight cut antenna. All radiators/radials cut to the exact same frequency.)

SWR measured right at the feed point. ZERO transmission line length.

First SWR set with the antenna trimmed to 27.2mhz.

(All readings have the “to 1” truncated)
26.00:2.0
26.25:1.7
26.50:1.5
26.75:1.3
27.00:1.2
27.25:1.05
27.50:1.1
27.75:1.15
28.00:1.2
28.25:1.4
28.50:1.5
28.75:1.8
29.00:2.0
29.25:2.2
29.50:2.5
29.75:2.9
30.00:3.2

That antenna would be usable up to 29mhz which would easily cover the N/T portion of the band 28.0 to 28.5

Second set, with the antenna retrimmed to 27.4

26.00:2.2
26.25:1.8
26.50:1.6
26.75:1.4
27.00:1.25
27.25:1.1
27.50:1.05
27.75:1.1
28.00:1.15
28.25:1.3
28.50:1.5
28.75:1.8
29.00:1.9
29.25:2.1
29.50:2.3
29.75:2.6
30.00:3

Again, that would get you past the 29mhz mark.with les than 2 to 1 swr.

Now we change the antenna design a bit. In the third SWR set, I set it up as a ground mounted vertical. Again with a 22 gauge vertical radiator and enough ground radials to achieve about a 20 ohm ground resistance. With the 30 some ohms resistance of the vertical radiator, it should get me right at 50 ohms resonant impedance.

Third set ground mounted vertical trimmed to 27.0 mhz

26.00:1.45
26.25:1.2
26.50:1.1
26.75:1.05
27.00:1.0
27.25:1.05
27.50:1.15
27.75:1.3
28.00:1.5
28.25:1.7
28.50:1.9
28.75:2.1
29.00:2.4
29.25:2.7
29.50:3
29.75:3.3
30.00:3.5

that 27mhz tuning still gets you under 2 to 1 at the top end of the N/T portion of the band.

Fourth set, ground mounted vertical trimmed to 27.5mhz
26.00:2.2
26.25:1.8
26.50:1.5
26.75:1.35
27.00:1.2
27.25:1.1
27.50:1.0
27.75:1.05
28.00:1.15
28.25:1.25
28.50:1.4
28.75:1.6
29.00:1.8
29.25:2.0
29.50:2.2
29.75:2.5
30.00:2.9

gets you to 29.25 with 2 to 1 swr. Which is right at the bottom end of the satellite downlink band. So you can cover about the entire point to point SSB/CW portion of the 10 meter band.

Now, for the fifth set, I changed the vertical radiator to a 1/2 copper pipe cut for 27mhz. Again, on the same ground plane. It will exhibit a wider operational bandwidth, more along the lines of what you will see in a normal real world factory cb base antenna built on aluminum tubing construction.

26.00:1.2
26.25:1.15
26.50:1.1
26.75:1.05
27.00:1.0
27.25:1.0
27.50:1.05
27.75:1.15
28.00:1.2
28.25:1.3
28.50:1.4
28.75:1.5
29.00:1.7
29.25:1.8
29.50:1.9
29.75:2.0
30.00:2.2

Which is about what I expected. Under 2 to 1 right up to the top of the 10 meter band (29.7mhz).
It will also be usable on the 12 meter band at around 1.6 - 1.8 to 1 swr.
Experience has shown me that an elevated ground plane using 1/2 inch elements will show about the same SWR spread, so doing that would be pointless.

If I cut the pipe to 28.25mhz, I should be able to get under 1.4 to 1 SWR across the entire 10m band and the cb band. All though, it would push it out of the range of the 12m band.

Now in the sixth set, I changed out the vertical for a center loaded whip.
26.00:6
26.25:3.6
26.50:2
26.75:1.3
27.00:1.1
27.25:1.8
27.50:3
27.75:4
28.00:7
in the seventh set, I changed it out to a top loaded semi truck antenna.

26.00:8
26.25:3.7
26.50:2.4
26.75:1.5
27.00:1.1
27.25:1.5
27.50:2.4
27.75:4.3
28.00:6

As you can see, the two loaded antennas show a narrower bandwidth. On those antennas, you would have to adjust them to usable SWR on 10 meters. And real world experience has shown me that if the antenna has an adjustment, then it can usually be pulled to 10 meters without any problem.

But for the full size unloaded CB antennas, they will be perfectly usable for 10m out of the box.


As I have stated before. After you have had enough experience, results will become repeatable. I already knew about what I would see before I cut the first wire. Sometimes you just have to put real world data in front of someone before they will come to grips with reality. Even then, they will often try to find ways to dismiss it.

So, there is the data, right in front of your face, but you can believe what you want, if it makes everyone happy,

reply to post by Mr Tranny

this is starting to sound too much like a pissing contest

Yes it is.

Your results are about what I would expect as well, and (probably) perfectly within operating tolerance. The only difference in our posts, which I have been trying to get you to understand, is this: you are presenting information that someone of our experience can use. I am trying to present information that a novice can use. Either of us can effectively operate the equipment you are talking about with no issue, but that is because we understand the limitations.

A novice just looking to get into ham radio probably does not understand all this yet.

As I said, your results are about what I would expect... the SWR forms a parabolic curve with the apex at 1:1 on a specific frequency (the matched frequency). On either side of the matched frequency, the SWR shows some mismatch (not to be confused with a dangerously high mismatch) increasing at an increasing rate the farther we move from the matched frequency. That's just antenna design.

But here's the caveat:

First SWR set with the antenna trimmed to 27.2mhz.

Second set, with the antenna retrimmed to 27.4

Third set ground mounted vertical trimmed to 27.0 mhz

Fourth set, ground mounted vertical trimmed to 27.5mhz

If the antenna is trimmed, of course a CB antenna will work on a large portion of the 10-meter band. That's your position and it is correct. But if a CB antenna is not trimmed, it may not work over all of the 10-meter band. That's my position and it is correct as well. The two positions are not mutually exclusive.

It's the difference between an experienced operator making adjustments and verifying operation, and a novice buying something and plugging it in. No disrespect to any novices out there is intended; everyone has to start the learning curve somewhere.

Incidentally, I am not sure about ham equipment, but I do know CBs are not all created equal. Some will handle a greater than 2:1 SWR with no problems, while others will start overheating at 1.7:1 - 1.8:1. Not everyone uses the same design for the final amplifier stages, and not everyone uses realistic tolerances when specing components. That's why I strive for a 1.5:1 maximum, although I will admit it is difficult to maintain across the entire CB band.

Can we agree that with proper adjustments a CB antenna may be used over a portion of the 10-meter band, as long as the operator understands the basics of antenna design? I'm running out of piss....

TheRedneck

reply to post by intrptr

You could try parking on a mountain top

Hehe...not in Florida......
No mountain tops here.....

If you get the right CB unit, and tweak it out, you'll get about 12-15 miles. I heard a couple guys talking the other day (well heard one of them anyway, he was close to me), and one of the drivers said he was going the other way, about 15 miles down the road, and was hearing this guy talking back to him, and being heard easily.

I do use HAM radio, exta class license

reply to post by Mr Tranny
true but using a 75ohm for ham will cut down on Rf back ground noise cleaner reception when doing CQ one of the best ham antenna, home made is , a TV antenna with UHF www.sedan.org... yes I did have a Ham lin , but it is no longer valid . thinking about getting a new one wireless.fcc.gov... but the if is like the net er web why bother, got the parts to build a 10 m base unit when SHTF any way so why spend money on something I would not use , but will give advice or free.