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Old 07-03-2017, 8:25 PM
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Default Whats a good starter SWR meter?

I have a 40 metre (BaseX? forgot what it was called, its a 60$ kit that comes from india, with just the board and arduino controlled LCD/radio) ham radio and It puts out 7 watts and is connected to a ~68' length of wire with a 9 or 11 balun (seems like a low power one maybe a receive only but my chinese isn't very good so I don't know much about it, or how to read the specs) and a ground. I see some really cheap SWR's but are those not worth buying?

I accidentally shorted out the TX switch and left it on TX for 3 hours. Radio still transmits I can see it on my SDR, but I don't know if it was damaged. power supply was warm but not hotter then usual.
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Old 07-03-2017, 8:58 PM
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I am fond of my Diamond SX 200 its been with me since christ was a corporal , i love the little guy , but be warned there are 2 different versions of it one does HF thru UHF the other leaves UHF out , if you hook it to your PS it is lighted but does not require power to funcbtion. You can buy something cheap and Chinese these days ,but you get what you pay for, Diamond is quite good and fairly inexpensive .

I have a buddy who accidently left his cat in the shack , he uses a straight key as a PTT the cat took a nap putting out about 400 watts of nothingness for about four hours , hasnt made that mistake again !
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Last edited by wrath; 07-03-2017 at 9:02 PM..
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Old 07-05-2017, 4:52 AM
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Are the one priced under $50 any good, or are they just a waste of money?
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Old 07-05-2017, 7:21 AM
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In my opinion, hams pay way too much for fancy SWR meters.

SWR meters are really pretty simple. A diode, a meter movement, and a few other components. The trick is building one that is flat across all frequencies of interest, building that will be robust enough to handle the RF current involved, and building one that can take the physical abuse that they often receive.

If all you are looking for is SWR, then keep in mind that you can get that by comparing forward and reflected power. In other words, it's a ratio. If your meter measures forward power inaccurately, who cares, because it's probably going to measure reverse power inaccurately, too. But, you only care about the ratio so the inaccuracies are not that important.

A cheap SWR meter made for CB radio will work just fine to measure SWR on HF. Just don't count on it to measure power because a cheap meter probably won't be very well calibrated. And, don't put it in your kit bag and toss it in the back of your truck because the meter movement probably won't take too much of that abuse.

All that said, you can learn a lot about your antenna from an antenna analyzer like the ones from MJF, Comet, and Rig Expert. If you are into building antennas, buying an antenna analyzer is a good investment in your future experiments. But, if you just want to check that dipole you put up to see if it's going to be a reasonable match to your transmitter, there's no need to over-do it.
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Old 07-05-2017, 3:14 PM
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I agree that SWR meters have gotten out of hand price and feature wise. Just read the specs-if they cover the frequencies you want and work with the power your transmitter is putting out you are good to go. That said think about what you may want to do in the future. You do not need digital readout or anything. For the most part If you are reading under 2:1 and are at a minimum you are good to go. If you have a local club you can ask around and likely barrow one. One of the 'mods' (or add ons) for your radio is a SWR function-might do some Googleing.
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Old 07-05-2017, 4:36 PM
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If you are interested in low cost, here are a couple of cheap ideas for you:

Just build a resonant dipole cut for the portion of the 40 meter band where you intend to operate and it will be close enough. In other words, don't sweat the SWR.

Don't have any experience with the BitX40 (sounds like that is what you have) myself but perhaps a light bulb that can handle 7 watts can be used as sort of a dummy load and rf output indicator. Check around with the BitX community and see if this is feasible.
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Old 07-06-2017, 10:34 AM
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Quote:
Originally Posted by WA8ZTZ View Post
If you are interested in low cost, here are a couple of cheap ideas for you:

Just build a resonant dipole cut for the portion of the 40 meter band where you intend to operate and it will be close enough. In other words, don't sweat the SWR.

Don't have any experience with the BitX40 (sounds like that is what you have) myself but perhaps a light bulb that can handle 7 watts can be used as sort of a dummy load and rf output indicator. Check around with the BitX community and see if this is feasible.
Seriously? That wouldn't get the SWR all wrong and dump power back into the radio? Has anyone actually tried that?
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Old 07-07-2017, 7:41 AM
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Quote:
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Seriously? That wouldn't get the SWR all wrong and dump power back into the radio? Has anyone actually tried that?
If you are referring to the use of a light bulb as a dummy load / rf indicator, my suggestion was to ask around the community of users of your rig. Light bulbs have been used for years in such fashion on all manner of QRP rigs but cannot say for sure if it would work with yours... ask around.
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Old 07-07-2017, 9:00 AM
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Very true about the light bulb trick. Back in the early '60s my ham friend showed me that trick. It let him know the transmitter was working without sending a signal out into the ether, plus other info.
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Old 07-07-2017, 12:42 PM
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I agree with W9BU that many hams over buy SWR meters; its as if you must have the highest end antenna analysi'zer to insure success. An SWR meter is simply a device that indicates forward v.s reflected power. Its up to the operator using their wits to determine what those numbers mean, and to use the device properly.
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That said, all power ratio meters (aka SWR meters) are not created equal. As the frequency increases, physics starts to play some dirty tricks. Introducing a meter into a line can cause miss matches, which of course can affect the readings, The meter itself by virtue of its design can have factionated wavelength components that can give very erroneous readings-- a case in point: try and use one of those inexpensive meters sold for CB to adjust a, say 440Mhz antenna.... a guaranteed heart breaker.... they work fine for HF up to 50 Mhz, but don't take them higher.
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I have several meters- my work place standards are four beautiful Bird 43P's- and these are not to be confused with SWR meters-- the Birds are watt meters, although everyone knows reversing the slugs shows the reflected power. Even for laboratory use, they are sometimes overkill... in the field, about 95% of the time a simple (cheaper) meter would work fine.
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Not long ago one of these 43's went missing during a field trial-- the meter and its expensive slug collection. No fingers were being pointed- stuff like that happens- but I had to write up a property loss, and submit it to the guys "without a sense of humour"
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Before any water boarding was done, the meter was found; it was just overlooked in the trunk of a vehicle- but it got me thinking about why we were taking thousand dollar meters (when you add in the slugs) out of the lab. So I went on Amazon and bought a couple of Nissei (RS40, 140-500 Mhz) and some assorted other SWR meters for a fraction of the Bird costs. Comparing them side by side they're readings were very precise. Every one now has their own--- and if a meter comes to grief, petty cash can cover the loss,- the Birds only go out when they are truly needed.
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The ham that likes to build - 'homebrew'- can certainly construct a bridge that rivals anything expensively commercial. I have old ARRL Handbooks showing just such designs- dating back to a time period where amateurs either built it or went without. I would suggest to anyone serious about antennas to take a scientific approach to this SWR topic, and research it throughly; maybe look into building their own- and don't think that that meter will magically fix antenna woes.
.
Want a challenge? I'll leave you to ponder the measuring SWR's at the ++ W Band Microwaves. If you've a good, simple way, Private Message me.... I'm struggling here... (laffing)
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............................CF
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Old 07-07-2017, 1:50 PM
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Quote:
Originally Posted by KC4RAF View Post
Very true about the light bulb trick. Back in the early '60s my ham friend showed me that trick. It let him know the transmitter was working without sending a signal out into the ether, plus other info.
Light bulbs as dummy loads have some serious drawbacks -
- They do radiate pretty well ("sending a signal out'). Many accounts out there from hams making QSOs over several hundred miles with a lightbulb.
- Typically the way a light bulb is hooked up as a makeshift "dummy load" is in a manner that puts the RF output right next to you or other people near the transmitter. Seldom a good idea, sometimes even very hazardous. At 7 watts it's not likely to be a human hazard, but may introduce RF into other equipment near the bulb.
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Old 07-07-2017, 6:22 PM
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Popnokick makes excellent points.
.
I will add that the RF resistance of an incandescent bulb is essentially unknown. Its a combination of a myriad of inductances, resistances....all frequency dependent. In the days of tube transmitters, especially those with Pi-Net outputs, those transmitter could be dipped to match just about anything....from single digit Ohms to the thousands--- that is not the case with modern solid state radios. Also as the bulb's light grew in intensity, the Ohmic value changes-- you have to 'track' it by varying the tuning as it heats up,,, and never take your eye off the colour of that PA's tube(s) plate(s)!-- it could go from a dull red to a fiery yellow in a heart's beat.
.
I "cut my teeth" watching my father and grandfather using light bulbs as dummy loads. The neat thing about them; if it was a 100 watt bulb, and you lit it to full brilliance plus plus, you knew your 'homebrew' was all of that 100 watts... no watt meter required.
.
A favorite "dummy load' for V/UHF QRP transmitters was (still is in my lab,) a #47 pilot bulb. As my grandfather would say:
.
"If you can light a pilot bulb you can talk to the world"
.
But I would not suggest them today unless you are a knowledgeable experiemnt'r.
,
For QRP a 50 Ohm resistor works great. If a 2 watt'er burns your fingers- well, its at least 2 watts...... Your Coyote Basic Wattmetter...
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........................CF
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Old 07-08-2017, 3:52 PM
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You can get a SWR meter on Ebay or Amazon for under $50.00. Make sure it covers 40 meters and doesn't need much to set (say a forward power range of 10 or 20 watts). Also remember you will need to transmit a tone on SSB in order to set and read the meter.

The light bulb trick of the past was ok if all you wanted to know was if the transmitter was 'putting out', but that is all. It did not 'check' the antenna system at all. Thanks for the trip back to my HW-101 days...
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Old 07-08-2017, 4:12 PM
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A cautionary tale...

Many years ago when the ink on my ham ticket was barely dry, I had set up my station under the house with a used Yaesu FT-901D, a KDK FM 2030 2m rig and for listening at work a used Icom 2a 2m handheld. A trap vertical worked well on HF, getting into Europe on the gray line on 80m, all I was allowed for the 6 months until I was deemed to be "proficient".

Anyway, I thought the Icom 2a was a little down on power, so I coupled up the Swan SWR meter into a proper 50ohm load. Took the back off the 2a, and with my golden screwdriver, tweaked all the coils in the transmitter side for max smoke in the meter. Hey, lookee, another 2 watts - should go great now...... that's funny, I can't hit the repeater...called my mate down the road who I knew would be listening...no answer...hmmm....

Took the rig to work to test on the Marconi power meter, sure enough 7watts instead of 5..must be good. One of the "old hands" was watching and asked what I was doing. I explained all and he said "Ah, yes, 7 watts but what frequency?". I looked at him blankly "how can it not be on 2m" I thought. "Let's put it on the spectrum analyser", said the OH. Lo and behold, lots of spikes of RF all over the place, but only a very small one on 2m. "Hope you didn't annoy too many people, you may have 7watts but it's spread all over the place" said OH, " lets tweak for the maximum spike on 2m and get rid of all these sub-harmonics". Back to 5watts now and on 2m too! Contacts a-plenty into the bargain!

The design of the handheld was a common one where the deviation is applied at a low frequency, then multiplied up to 144MHz to get the full deviation. Unfortunately I had tweaked the multipliers and got the power on the lower frequencies!

The moral of the story - not all power is good power! ..... to paraphrase Lord Acton.
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Old 07-08-2017, 4:39 PM
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Back in my CB days I had one of these hooked up. An RF ammeter from an ART-13. Pretty neat!

http://i.ebayimg.com/images/g/Ne8AAO...whm/s-l300.jpg
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Old 07-09-2017, 12:23 PM
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An RF Amp meter!
.
Neat subject; measuring the actual power component to the antenna's input. One of them in concert with an RF Voltage meter is bit exotic for the average ham... after all, just knowing the relative v.s actual power output from a transmitter is sufficient 99.99% of the time. Or is that still the case?
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I am referring to the two new bands, as yet to be awaken'd (in the US)- 630 and 2200 meters. Especially the later. With the severe limitations on effectiveness of antennas, guaging a station's performance is quite a challenge. I have a 136Khz station set to go, with what I have *calculated * to be 1 Watt EIRB.. but that's just what the computer** says... Finding an in-line watt meter to measure the actual power between the loading circuit tank and the antenna at Tesla Coil like voltages has proved a real challenge***
.

I have, however, stepped back to the Golden Days of longwave and put a RF amp meter- very well isolated from ground, mind you !, -- in series with that antenna feed. I don't get anything meaningful from its readings- but I find it fascinating to actually see, - in-the-flesh,- just how little current is flowing at RF voltages that I can only guess at..... ie: by how big of a spark I can draw off the loading tank coil (its Big!)
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I didn't mean to digress- but this topic- SWR and measuring antenna parameters is a lot more involved than simply using an SWR bridge.,, No?
... And just as involved as it becomes- so does the fascination for the radio science behind it. Did anyone happen to mention measuring the actual magnetic fields (as opposed to the electric) that surround a radiating antenna? Think your radiation pattern is all pure and textbook?.... want a little something else to think about??............smiles....

.
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............................................CF
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**I am sort of jumping the gun on the opening day for 2200. But I was able to test (legally!) on a nearby frequency for 2 days- and determined that for 1 Watt E(I?)RP my 'after burner' of an amp will be set at 855 watts on 136 Khz.
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*** "Challenge" as in I have found better things to do with my time and have abandon'd this pursuit.
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Old 07-10-2017, 12:58 AM
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Tesla Coils .... reminds me of Bjork's performance art "thunderbolt" in biophilia. She had those suckers modulated with the bassline. I doubt any of it complied with Part 15, But I digress.

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Old 07-10-2017, 4:27 PM
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I don't mean to veer this topic off onto Tesla Coils... but they are, in their own way, a form of antenna... albeit a very high voltage exotic antenna.
.
This returns me to my RF Amp meter barely moving, meanwhile conducting mega volts of RF...... and this afternoon out on a site I ran across this MOAT (Mother Of All Transformers )
This transformer dates back aways; what is is interesting about it is its rating to 690 Kv's at 5.8 Amp's.---4 millon watts! Note the little amp meter in the aluminum box where the upper electrode connects... its only 10 Amps full scale. So much power thru so little current!
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Anyway, I was impressed.
When this thing was 'hot' you checked the current thru a pair of binoculars, standing back behind a cyclone fence!
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Using the formulae for a arc's discharge of:
.
Voltage= distance of spark (cm's) x 30K
.
...this "transformer" could assume the role of a Telsa Coil (noting especially its top insulator)
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This kind'a finishes me on this subject-- except to say I like to use the spark method on high power low frequency transmitters to impress our interns about RF. It can be very dramatic.
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..................CF
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Old 07-10-2017, 7:10 PM
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I can think of all kinds of crazy unauthorized purposes for that transformer. Put an electrode on top and wire the LV coil as secondary with a rectifier and charge a storage battery. Plug in your stuff to charge whenever you visit. Or Power it from a big audio amp and hold an annual rave concert at the site in honor of Nikolai Tesla.

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Old 07-10-2017, 10:44 PM
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Smiles !... what a Smashing idea!
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....................CF

Last edited by Coyote-Frostbyte; 07-10-2017 at 11:08 PM.. Reason: being a tad more expressive :)
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