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Can out of band transmit be harmful to a radio?

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Danny37

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I have a vx7200 that is 380-450MHz I was able to get it to go to 462.500 for GMRS. Could it in anyway effect the radio?
 

zz0468

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That would depend on the specific radio. For example, some 100 watt class amateur radios can be opened up, but have internal bandpass filters that would be forced to dissipate power levels outside their bandpass that they're not intended to deal with.

I doubt your radio would be hurt. It just might not work well on out of band frequencies. Just because the display says it's on that frequency doesn't mean the hardware likes it there.
 

K8LEA

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Danny:

One other thing.... ZZ0468's correct, IMHO, but some of the newer synthesized radios will display one thing, and transmit someplace else entirely.

IMHO, most handhelds (5 watts or under) will likely work well enough that far out of band, but internal losses (and SWR issues with the antenna) may reduce performance somewhat. Plan on it....

ALSO, let's not forget that using Ham gear on commercial frequencies is generally a no-no. I don't know about your radio (if it's a commercial unit, there's no issue), but while I can make my ancient Yaesu FT-23R transmit from something like 130Mhz to 170Mhz, it's not type approved for commercial use, and a violation.... The commercial version has a little cover plate on the "panel" that restricts the user from changing frequencies, but appears to otherwise be the same radio, but cost at least $100 more (something like 20 years ago).

Regards,
 

Danny37

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What about for recieve purposes? This radio is actually a friends it's commicial gear part 90 cert but he's a licensed GMRS op so I was able to program the GMRS but its more 12MHz out of band. He's going to be using low power so I think he's good. When should I be on the look out if the radio decides to shift? After prolonged transmission?
 

K8LEA

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Danny:

The receiver doesn't care what sort of antenna, or how far out of band. Sensitivity may be impaired (or even improved!), but who knows. IAC, receive mode won't cause any issues unless you've got a high power transmitter handy, in which case even a dead short across the input may not be helpful :D....

Reminds me of a now-deceased buddy who was given a nice HT by the Radio Club as a retirement gift. He was having battery issues, so he decided to leave the thing switched on "low power" even when only receiving. He never quite figured that out....

Joe, btw, ended up with a couple of pacemakers and all kinds of cardiac issues. He showed up at one of our lunch meetings one day - the kind where everybody's got an HT on the table and the waitstaff can't quite figure out which drug agency we represent ( :D ). So, as Joe sat down, I asked him to turn off his pacemakers 'cause they were interfering with our reception....

The radio won't necessarily shift frequency by itself (unless it doesn't like the operating temperatures, which may cause some strange things before it goes off to heaven), but a lot of them will indicate other frequencies than where they're set when set out of band.

Funny thing - the VX-150 is the first HT I remember hearing about cooking off with the wrong antenna - there apparently was a run of them where the final transistors didn't like that at all.

Now, I did have (come to think of it, it's in the office downstairs someplace) a "Brimstone 144" which operated on 2M using three ten-position rotary switches to set transmit frequency, and three others to set the receive frequency. You could also set simplex on one of the others if I remember right. The switches went to a "converter" board that turned their settings into a binary representation that told another board what to tell the VCO you really had in mind. ("VCO" is "Voltage Controlled Oscilator". The simplest analogy I can think of is a motor turning your tuning knob, with the voltage telling the motor how far to turn.) Anyway, a local Ham repeater on 147.375 just didn't sound right. Clearly off-frequency if you were used to that sort of thing. Didn't seem right. One night, and I don't really know what got me started, I yanked the decoder board and stuck it on a test bed. Stuck in all the possible inputs, and logged the outputs. Worked fine.... Then I did it with the next board. Hoohah.... Anything with a "7" in that position resulted in a ZERO, so "147.375" was coming out as "147.305".

Turned out to be a bad solder joint. The board was double sided, and one pin of an IC was only soldered to one side of the board. Quick touchup with the right iron and all was well, and it only took me a couple years.... :D

(The "Brimstone" was made in Kansas, and nearly bigger than a breadbox. Back when everybody was stealing radios - going for CB's - nobody in Kansas was even locking their cars. IAC, in case you're wondering why that "7" thing made it out of QC, the Brimstone receiver - unless you spring for the "urban" model - was very sensitive, and had little selectivity. VERY little.... :D .)

So, within the "where's the radio really operating" issues, you can receive anything you can talk the radio into. Transmitting outside of the design parameters, besides maybe being illegal, is kind of iffy. Low Power will help, though. I have a Kenwood TH-F6A that can be "opened" roughly from DC to visible light, but get a ways out of the original bands and the thing complains and refuses to transmit.

Low power, what you're trying to do ought to work fine. You may want to find an antenna that's spec'd for that frequency range.

Regards,
 

Danny37

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That you've been so helpful, the antenna he's using is 400-470 so I don't think it'll mess with it at all.
 

kg4ley

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That you've been so helpful, the antenna he's using is 400-470 so I don't think it'll mess with it at all.

The only thing i have found in out of band is a loss of power,swr really wasnt a factor so if you can deal with the power loss it should not be a problem.
 

Danny37

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The only thing i have found in out of band is a loss of power,swr really wasnt a factor so if you can deal with the power loss it should not be a problem.

How much loss? If 5 watts is being transmitted, how much will it be out of band? 4? 3watts?
 

kg4ley

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Depends on far you go.Some freqs will go up some down.With all the high power ham vhf and uhf rigs out there being used out of band for fire and whatever else who is checking?
 

K8LEA

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Danny:

My old Icom IC280-H does something like 50 watts in the 2M band, and drops to 30 or so at about 150mhz. A buddy's didn't do that! I don't know whether he got an EC or just got lucky. :D

(You can run these things into a dummy load legally, IMHO, and at "low power", they make half-decent signal generators for testing - forget about alignment, though, unless you really know what you're doing, and have a "standard" to calibrate the radio against.)

Just IMHO, the antenna and any tuning possible in transmitter's finals will make a difference when transmitting "out of band". The receiver likely has the same choices. Just IMHO, again, the commercial versions of these hi-band radios (such as the ones I have) put their "best" receiver characteristics at something like 160mhz if no tuning is allowed for, while the ham gear is is going to be best at 145-150 mhz. (Seems like there used to be a 170mhz variant available, too.)

Now, when you're talking about a 5 watt radio, which gives you a couple watts at the antenna, a few percent (while it might be significant in marginal situations) probably won't bother anything. The problem is, as I mentioned earlier, the design and fitting of a Rubber Ducky is a black art, and expecting one to work over the sorts of ranges that these scanners (or my TH-F6A) is already wishful thinking.

And, unless you're trying to go for distance records, you're usually not interested in that much output. Getting nearly full quieting (FM) into a receiver some distance away is good enough. (With FM, at some point, the incoming signal over-rides all of the noise that may be present in the radio, or out there in the world. Any more signal than that is wasted. (Can't say it's current now, but early Analog cellphones could "discuss" their relative signals with a base, and lower their power. This helped the efficiency of the frequency-sharing function inherent in cell design.) (AM does NOT let you do this. I'm not sure about SSB and digital, but it's likely that the digital signals run over NBFM.)

This can bite you, btw. Many years ago, Pittsburgh PA's PD and Youngstown OH's PD shared a common channel. 65 miles, give or take, so it really should not have been a problem. However, when propagation was just right, a PD unit wandering around Youngstown could often hear Pittsburgh's dispatcher. Problem was that Pittsburgh used no codes at all, and has street names that are very similar to Youngstown's. A lot of YPD cars went to the wrong location.... The Officers got into the habit of bending their antennas (19" spikes in those days) into a loop terminating in the slots around the trunk lid. Didn't always help hearing their own dispatcher at all, but the ancient tube-type radios in their trunks didn't mind it at all.... (Pittsburgh went to 450mhz somewhere along the line. Probably trunked by now, too. YPD sent in a grant request - before trunking was common - for about seven frequencies and all kinds of new radios. Granting agency laughed....)

Regards,
 

Danny37

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K8lea you've been especially helpful thank you so much! I hope your not getting annoyed with my questions lol as I'm a newbie to this stuff. What device can I use to analyze a portable radio transmit power?
 

zz0468

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What device can I use to analyze a portable radio transmit power?

A power meter designed for the desired frequency range and expected power range. Amateur grade power meters (aka watt meters) are relatively inexpensive.
 

Danny37

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Can you point me in the direction where I can find one for vertex/yaesu portable sma type radios, a search on eBay got me confused.
 

MTS2000des

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the only way to know FOR SURE what a radio is doing, is to put it on a service monitor with a spectrum analyzer, and verify the output. A SA will show you where the spurs are, and how much power is going where.

If you are using a piece of equipment outside it's rated design, it would not hurt to seek someone out who has a service monitor and put it on their bench and see for yourself.
 

jaspence

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Out of band

When you transmit out of band, you have no idea of what interference (harmonics) you may be creating. Many emergency services still use the 150 mhz and 450 mhz frequencies for comms and dispatching. Interference from an uncertified radio in these bands could be life threatening.
 

K8LEA

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Danny:

The guys have hinted.... :D

The problem is that any transmitter (and the synthesized ones are probably the worst offenders) can put out all kinds of RF at frequencies somewhat different from the "center" - usually what you've tuned it to when "in-band".

Usually, this stuff has very low levels, but some odd things can happen. For example, a transmitter tuned to 150.000mhz (round numbers :D) but not designed to work there, can provide a substantial signal at 300mhz. Might not bother anything, but who knows. Add to that the ability to put signals out at 150mhz + and/or - the 10.7mhz (likely) IF frequency, as well as all kinds of other combinations, and you've got a potential mess. Low-power gear may never bother anything, but a 75Watt transmitter may have some significant output at just the wrong place. (A spectrum analyzer really is the only way to fly.) The low-power stuff may wipe out a local PS frequency, too, if you're close to the receiver.

(Presuming that you're very close to the same frequency, an FM decoder will generally "hear" only the strongest signal on the tuned frequency. If the PD's on 158.73, and you're across the street from their receiver site, your spurious output may just wipe that receiver out - at least for HT's some distance away. Needless to say, this will make nobody happy. Type-accepted radios are certified to keep these signals down to a certain level. The Amateur Radio version may have some of that missing.)

Some decades ago, I was a student at Case Institute in Cleveland. I took a 6M AM (Ham) transceiver along, and set it up in my dorm room. (It was fairly easy to pop an antenna out a window as needed.) I'd learned that there was a net on 51.000Mhz and brought crystals (remember those? :D) along for it. I used the radio elsewhere (51.000Mhz, while well in-band, was kind of off-the-edge for most people in 1963) with good results. Tune the thing to 51.000Mhz and I found extreme noise between about 50.7 and 51.5Mhz.

It took a while to find it, but it turned out that TV Channel 3 was active in Cleveland, and the video carrier was more or less exactly at the local oscillator injection frequency, and riding through the receiver, causing the noise.

(Before anybody yells - I don't recall if the TV carrier was 10.7 mhz above or below the 51.0mhz target. The idea was to mix the a local oscillator signal with the 51.000mhz signal, and then further process one of the mixing results as if it was an "original" at 10.7mhz. In many cases, another mix is done to put the incoming signal on 455Khz, and in some cases only one such mix to 455Khz is done.)

In this case, a simple trap on the antenna cleared the problem up, but what if I'd been an ambulance service?

The trap? You can combine a capacitor and an inductor so it's a dead short at a particular frequency (which sort of kills any signals coming into the receiver there) but effectively not there at all at other frequencies.

Slightly more recently - say "before 1970" - a friend of mine and I got volunteered to install a new sound system in his Church. My friend lived down the block from the Church, and was a sort of unofficial sexton.

We spent a few bucks, and set up a slick system that'd let 'em remote the Sanctuary audio into the basement social hall/overflow area, with separate level controls, monitoring speakers, and all kinds of magic stuff. Worked exactly like it should. (Sometimes even a blind pig finds a truffle :D.)

Then, come Sunday AM, as they rang the bell to start the Mass about 0700, the thing started playing music. Youngstown State University's FM station, at 88.5mhz, was only a couple miles away, and strong enough to turn up at the microphone inputs (even though the cable was shielded). In those days, WYSU was on a restricted schedule, and it just happened that we'd not been working on the thing while they were on the air....

The fix? Simple, but I couldn't do it for a couple days. You grab a handful of small capacitors, and while playing with the length of the capacitor's leads, you try to find a combination of capacitor value and lead length that shorts out the 88mhz signal without any effect on the use of the amplifier. Turned out to be pretty simple - it almost took longer to pop the covers off the amplifier.

That, btw, is part of the "no cellphones on airliners" view. From a practical standpoint, the aircraft probably is immune, but it's not necessarily been tested for the frequency that your phone may select. Not to mention the possibility of using multiple sites on the ground at the same time. Gotta be hilarious to bill.

The short answer is that "yes, it can".... :D If a radio hasn't been "opened up", especially if it's type accepted, it should not cause problems. One that's not type accepted, and opened, it's hard to say what will happen.

Regards,
 

N4KVE

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Years ago when the Icom 2720H first came out, I purchased the 1st one in Ft. Lauderdale. The tech at the radio shop did the mod to open up the radio. Testing into a dummy load, he found the tx power dropped to 5 watts above 455 mhz, but would work up to 520 at 5 watts. However on the low side, it put out full power right down to 400 mhz. Actually, the power increased as the radio got below 420. Of course this was just for testing purposes so the tech could document the figures should another customer ask what the coverage would be.
 
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