SWR - Readings dependent on EXACT coax positioning

[Colin9690]

First of all, I know this isn't how it's supposed to be done. I'm installing it in my vehicle in a few weeks. So for now, my radio is running off a proper AC power supply hooked up to a Wilson 1000 mag mount on top of my large steel Sentry safe.

According to my radio, I'm able to achieve nearly perfect SWR if I have the coax positioned a VERY specific way. Sometimes moving it by a millimeter, or nudging it will change the SWR drastically. Has anyone experienced this? This is referencing the radio's built-in SWR meter. To produce good SWR, the coax likes to be laid out in a loose coil on the floor. Thru trial and error with the coax positioning, I end up with good SWR. But I hate the fact I have to keep messing with the coax for SWR to not get out of control.

Lastly, could I (semi-permanently) leave my external SWR meter hooked up while using the radio? In effect, referencing my external meter vs the radio's meter. Just wanting to make sure this won't damage the meter.

 

[slowmover]

There’ll be an explanation forthcoming, but I’d leave well enough alone till installed on car.

Get the tool:

Astatic PDC1 Kit

Check out this Walcott Radio PDC1KIT at www.WalcottRadio.com

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A separate meter is SOP.

.

 

[mmckenna]

Mag mount and your safe are not providing a suitable ground plane. That results in the coax acting like a counterpoise. Movement of the coax impacts the counterpoise and thus your SWR.

Totally normal. To be expected in the situation and you may see that happen when you mag mount it on the roof of your vehicle.

 

[WSAC829]

mag mount on top of my large steel Sentry safe

As mentioned, totally normal. Your safe would have to be roughly 8 feet x 8 feet or larger, or you could attach a 1/4 wave wire to the ground portion of the antenna to act as a counterpose rather than the coax being the counterpoise.

 

[niceguy71]

As said before, without the proper ground plane the coax acts like a ground plane.... It's not really a ground plane... It just fools the swr meter
Question... Is the antenna inside the house??? A CB antenna will not work inside a house ,.. the house blocks signals from going out and coming in ,... When you transmit the signal bounces all around inside the house and is not healthy for you.

 

[wtp]

it sounds like ^niceguy71^ lives in a faraday cage...

 

[WSAC829]

Right? Guess he’s never heard of attic mounted dipoles, or people stuck in apartments putting mag mounts on cookie sheets, chest freezers, etc. I once talked to Wales England with a K40 stuck to the top of my stove years ago. It also worked well locally when i was living in a rental unit back in the day with no option to put an antenna outside.

Not HF/CB related, but my N9TAX dual band slim jim hanging from the corner of the my man caves ceiling hits repeaters 40 miles away easily.

 

[BinaryMode]

A CB antenna will not work inside a house ,.. the house blocks signals from going out and coming in ,... When you transmit the signal bounces all around inside the house and is not healthy for you.

Not really for 11 Meters. When you go up higher in frequency they tend to bounce off things. Like 802.11ac or 802.11ax Wi-Fi. That's why you need a mesh system in the house for such bands. And it's probably why a good majority if not all Wi-Fi cameras and other IoT stuff only uses 2.4 GHz.

And no, while I'm certainly no expert, 11 Meters isn't like some kind of "radiation" that will harm your cells in the skin. Unless of course you use 100 some watts! behind it. Then they teach you about duty cycle... Well, as it pertains getting a Technician ham license that is.

 

[RichardKramer]

When you transmit the signal bounces all around inside the house and is not healthy for you.

27MHz freqs won't hurt you inside bouncing around the house; I'd be more worried about being in the same room while cooking something in your microwave oven; microwaves are what you don't want bouncing around the inside of your house that are unhealthy.

 

[niceguy71]

it sounds like ^niceguy71^ lives in a faraday cage...

If I take any of my handhelds and put on a 51 inch telescoping antenna and stand outside my house with scan turned on I receive lots of people especially on channel 6 ... 9.... And 11....
But as soon as I go in the house absolutely nothing!
I like to leave my president Randy on my coffee table on scan ... Been there a couple years... If someone is within a mile I'll pick them up but nothing more.... If I go outside I hear everything
Anytime someone buys one of these gimmicky inside antennas they never work..... The attic antennas seem to get 3 miles. And that's with the antenna stapled a foot from the roof.....
every YouTube video I've watched on the attic dipoles or others things people do they always say they can get 3 to 3.5 miles.... That to me means it's not working very good at all..... Seems like a waste.
The main floors of a house have sheetrock on all the walls.... It acts just like rock... The signal will be terrible for transmit and receive.... Just like you can't use a handheld CB inside a car ... It won't transmit or receive more than a 100 feet. If you don't believe me try it.... I've tried both, the car and the house.... They don't work and it will throw off the swr

 

[kc2asb]

Indoor antennas do work! When I first got into CB during my high school days in the late 80's, the folks would not allow me to put up an outside antenna. The local CB/scanner shop had a Firestik indoor base antenna, which was a 5-foot whip with the tunable tip, screwed into a base with four flat steel bars acting as the groundplane. SWR was fine - about 1.5 or lower across 1-40.

I put it up in the attic (3-story wood-frame house) ran the coax down, and I was able to talk about 4-5 miles locally. As for skip, I made a number of contacts in the midwest and southwest. This was during an especially active sunspot cycle (1989 - 1991 - Cycle 22?) When the skip came in, I could not hear a local 4 or 5 blocks away None of the cycles since then have been as good, IMHO

 

[niceguy71]

Indoor antennas do work! When I first got into CB during my high school days in the late 80's, the folks would not allow me to put up an outside antenna. The local CB/scanner shop had a Firestik indoor base antenna, which was a 5-foot whip with the tunable tip, screwed into a base with four flat steel bars acting as the groundplane. SWR was fine - about 1.5 or lower across 1-40.

I put it up in the attic (3-story wood-frame house) ran the coax down, and I was able to talk about 4-5 miles locally. As for skip, I made a number of contacts in the midwest and southwest. This was during an especially active sunspot cycle (1989 - 1991 - Cycle 22?) When the skip came in, I could not hear a local 4 or 5 blocks away None of the cycles since then have been as good as that one, IMHO

You placed it in the attic.... I can see that working a few miles.... It just has to go through the roof and shingles
... I believe the original poster had a magnetic antenna on a safe in the house ... Meaning sheetrock walls... Highly unlikely the safe was in the attic

 

[K9KLC]

What some people call working others would never consider working for them. All depends on what you want to do. Skip can be worked on a light bulb if conditions are right. People do what they have to do to get on the air which is great however comparing some of this stuff to a bonified external antenna, properly installed with good coaxial cable (or other feed line that's appropriate) is just not the same. As I said in another post "if it's working for you then it's working for you and that's great." Doesn't mean it will fall under everyone else's definition of working. (for them).

 

[kc2asb]

You placed it in the attic.... I can see that working a few miles.... It just has to go through the roof and shingles
... I believe the original poster had a magnetic antenna on a safe in the house ... Meaning sheetrock walls... Highly unlikely the safe was in the attic

Yes, it would work better in the attic of course. I had it in the middle part of the attic, which was open to the joists and base of the shingle roof. However, there were two bedrooms up there on either end with plaster on lathe walls.

When I finally was allowed to put an Antron 99 on a 30 foot mast in the yard, the locals said the difference was night and day.

Certainly the construction type of the structure makes a difference, such as a steel-reinforced concrete building vs a wood-frame house. I never used a handheld CB inside a car, but the steel body would obviously have an effect on received and transmitted signals.

 

[kc2asb]

27MHz freqs won't hurt you inside bouncing around the house; I'd be more worried about being in the same room while cooking something in your microwave oven; microwaves are what you don't want bouncing around the inside of your house that are unhealthy.

I'd rather have a 5 watt CB transmitting through an indoor mag mount right next to me vs holding a cellphone up to my head for any length of time.

 

[BinaryMode]

I'd rather have a 5 watt CB transmitting through an indoor mag mount right next to me vs holding a cellphone up to my head for any length of time.

I believe the legal limit is 4 watts. LOL

And yeah, no doubt. Holding a UHF xmitter near your head for hours everyday is probably gonna cause problems some time down the road. It's almost analogous to ionizing radiation where being exposed to a few rads isn't going to do anything. But continuous exposure all the time will. I have to wonder if flying for a living or being an astronaut has some limitations on this?

 

[wtp]

ok, now for some "things"...
this is in adherence to rules of thumb.
many homes are energy efficient which means wrapped in metal/foil.
the roof-
for decades they have made "solar" ply.
it is an aluminium foil faced plywood to reflect the heat away from your attic.
this also reflect radio waves.
it is supposed to be put up with the foil on the inside, but i have seen it done wrong with it on the outside.
so looking in the attic might not tell you it is there.
the walls-
to also keep you hot or cold, there is aluminium faced insulation. hard to see behind the drywall.
the windows-
if they look like mirrors, there is metal in the glass.
not like a sheet, more like little tiny particles.
the better the insulation value, the more it reflects heat/energy

so that is a quick breakdown as to why it can be hard to hear any radio reception in a house.
and explains why you have to go outside to hear it, or use your cell phone.
my daughter had to do that at the sister-in-laws new house.