#72: Simple Station Monitor for Ham Radio using an Oscilloscope

[@jeffreyyoung4104]

Your simple RF Sampler circuit is an unsung hero for anyone who wants to monitor AM and SSB signals!

[@pianoplayer8226]

Hi Alan - - I did something similar without the risk of damage due to switch in wrong position. I ran some rg178 thin coax through gap in my tuner housing to about 20 turns wire wrap wire on a wooden Q tip dowel for a pick up. Works great. -Art, NF1A

[@w2aew]

Sounds great, Art!

[@johninjersey]

An easier way is to just wrap a few turns of wire around the coax and connect to scope. More turns is more signal.

[@rualmet]

Was totally going to say that! I use 14” gator leads and wrap until it runs out, then stretch as far as I can while still being able to connect my probe

[@mrbeach3379]

Hi jersey john how do connect the probe and earth clip, probe to the turns of wire , clip to radio chassis? Do you have to use a particular gauge of wire

[@Orvulum]

You could put a preamp on the input of the scope too... with a little whip antenna. That's a common feature on communications service monitors.

[@RadioHamGuy]

Very helpful, I have an older 10 Mhz scope and because it was that, I didn't really consider it for HF since I didn't think it would work on the upper bands very well but after watching your other videos showing how they still do work much above the rated freq, just with a lower amplitude response and guess as long as I could see what the signal looked like, that is what I am concerned about, so might play around with that sometime, thanks, all your videos are very informative.

[@WA7PRC]

I've done the same thing w/o a tuner. A loop of wire a few feet in diameter works well. Mine consists of several test clips connected together and draped over the curtain rod. I also have several turns of wire wound around the coaxial feedline that does the same thing. Also, I have my Tektronix 2236 (100 MHz) set up with "Normal" triggering and the trigger level set /just/ above zero. Until the 'scope sees some signal, there is no display. That saves the phosphor coating inside the front of the CRT, and extends the CRT's cathode life.

[@BirdWhisperer46]

"set up with "Normal" triggering and the trigger level set /just/ above zero. Until the 'scope sees some signal, there is no display." I've got the 2247A. I will have to try and figure that out. I also use the wire wrap on the COAX. Works a charm.

[@BaldurNorddahl]

I am just using a T adapter to route the signal by the scope. Only doing this for my low power DIY projects as high power could be too high voltage. I checked the datasheet for my Siglent and it can do 10 V per divison at 1:1 (= 80V) and survive up to 400 V peak. Could also unplug the T and use a 10:1 probe for an ugly solution that would handle a lot of power (> 1 kW) but still show the signal sampled directly and thus the correct voltages.

[@Sky1]

A reason to take my scope out of the shed and give my shack that high tech cool factor!

[@clems6989]

I tried it with my old Tech 2225 and it worked fine...Thanks !

[@M1bcm-ham-radioCoUk]

Excellent, i bought an old scope a few months ago with the intention of learning how to use one, but when i realised i couldn't monitor my own signals with it, i kinda left it on a shelf. But now you've solved my problem for me, this is my project for tomorrow. Love your video's and as you can probably see, i've subscribed to your channel. 73 Jeff M1BCM

[@w2aew]

Jeff - you may want to take a look at this video on a VERY simple RF sampler that you can use with your station... Simple Station Monitor for Ham Radio using an Oscilloscope Or this one on additional RF Samplers: Basics of RF Samplers, Sampling-Tees, RF-taps, etc.

[@M1bcm-ham-radioCoUk]

***** Well the first one is the same one that i commented on, i have the 2nd one cued up for watching tomorrow. Question: With the simple monitor lead connected between the scope and ATU, altho i'll have RF power turned right down at the beginning of transmission, what level of RF is usually adequate to trigger the scope/waveform ? Jeff M1BCM

[@w2aew]

Jeff, it will depend on the tuner that you use. Different tuners will have different amounts of RF coupling to an unused antenna port. Make ABSOLUTELY SURE that you do NOT transmit directly into the scope. On the few tuners that I've tried thus with, even 5-10 watts going to the antenna or dummy load was sufficient to get a readable signal coupled to the un-selected port used for the sampler.

[@M1bcm-ham-radioCoUk]

OK on the 5-10w, but i have to point out, i don't use a tuner, neither does anyone else as what is termed as an ATU doesn't "tune" the antenna, it merely fools the radio into thinking it's been presented with it's expected 50ohm input. The more correct abbreviation should be an AMU. That's why i call it a "matcher" lol

[@w2aew]

Of course it doesn't "tune" anything, it is merely an impedance matching network. I see nothing wrong with using a transmatch. You've got to watch out for feed line losses between the transmatch and antenna, but if you use open wire or twin lead, then this is a non-issue. It's really no different from the old plate and load adjustments on a tube tx or amp, or a gamma match at an antenna feed point - their all just different ways to provide impedance transformations to effect maximum power transfer.

[@zoolkhan]

You can also take a cable out of your scope, and curl it around the antenna-coax. (10-20times perhaps?) That will be enough. No risk of ever transmitting into the scope. I use an old audio-cable i had flying about, but there is certainly better options. You could take a peace of coax, and curl the center wire around the antenna-coax - but the trip from there to the scope remains shielded (shield to ground - center wire to scope channel X)

[@w2aew]

Yes, this works great as well - another fantastic zero-cost/parts solution.

[@jonramleth4727]

@@w2aew I simply used a 50 ohm resistor straight on to my scope probe and that picks up plenty. But it is not so easy with just RF to adjust modulation. with your sampler and trapezoid pattern is better. Even better if I had a two tone audiogenerator. Any tips on building a simple two tone?

[@cameronturner7475]

I have an older micronata power/ modulation/ swr meter that has a 1/8"monitor jack I just use a little pig tail and clip my probe to that.

[@pottypete5593]

Im going to try that. Thanks for the comment.

[@ward5821]

I am using a circulator that I removed the shunt. Then you have turned the circulator for UHF into a an RF sampler for the HF bands.

[@Radiowild]

I never would have thought about doing that....... A stellar idea! RW

[@Ace-cl4tc]

This will also work on a antenna switch.

[@g0fvt]

This is a very handy way to sample, works fine for me. I have various "proper" samplers but they are often hiding. It is tempting to incorporate a dedicated sampling port on my atu.

[@w2aew]

+g0fvt Good idea - just install a BNC connector, and maybe just add a short bit of wire or loop as a sensing "antenna" inside the tuner - no need to connect to anything inside.

[@g0fvt]

+w2aew Exactly what I was thinking

[@gassytubes3643]

hehe..maybe, but I fried a nice freq. counter doing this (yes, I did it, accidentally set the switch to that port and pumped 25 watts into it)

[@earleclemans4836]

Hello excuse my ignorance but on the modulation do you just use mic gain to adjust? And what does the form look like when properly adjusted? I dont think o have flat topping and im very close to calibrated line on scope

[@ravenbarsrepairs5594]

Any reason not to open up the tuner and drill a new hole to mount the connector, then putting a wire inside the case attached to the connector? Essentially a short antenna inside the tuner to eliminate the possibility of ever transmitting into the scope.

[@w2aew]

Sure, that would work perfectly well too.

[@gatesmw50]

Where some confusion comes in is that you can transmit into some of the later service monitors. People see that and than think you can do that with these o'scopes. Personally I avoid doing any of that despite what IFR claims you can do.

[@Organplayer1947]

I just wrap a couple of turns of insulated wire around the antenna coax. One side goes to earth ground. The other side of the coil goes to the scope. Ezzy Pezzy. WA6PBJ

[@w7dtg]

what a great way to monitor your signal. Most ham operators already have antenna tuners. What type of scope would you need. Would a 5MHZ scope be adequate or would you need something better ?

[@1925sk]

Thanks, tried this with the SM 220 and worked fine. NL7IB

[@dombaines]

Bit safer... if do not have a purpose made sampler (I have made and used one the simple resistance samplers you show in the video) why not just wrap one end of the scope input feed about the TX RF cable? Take a simple BNC (RG174 or RG58 (thinner so flexible) patch lead, one end you connect to the oscilloscope channel the other strip back the braid for 4" or so and just wrap the centre about the coax, you should see a signal on the scope when you TX. This way you will not TX into your scope and you will still be sampling some of the RF going to the dummy load or antenna. We have all seen or used a clip on ferrite core over a feed line, you have asome wire wrapped about the ferrite and to a uA meter this indicates RF going through a feedline... this is exactly the same principal. Despte the warning I can still see someone if careless might put 5w or even 500w into their scope :-) 72 Dom M1KTA

[@Thujaplicata1]

Can you please point me to where the video is to make the RF sampler? Thanks!

[@merseyradar6881]

Thanks for this video Alan, Finding 1n34a genuine diodes is a challenge though. Could you recommend any alternatives that are more widely available please ? Great videos for the radio enthusiast, Congrats.

[@w2aew]

Schottky diodes can be used.

[@Gordonseries385]

Tape a Straight gimmick wire on the coax?

[@w2aew]

That works too!

[@caravanken1]

This video along with many of the others has taught me a great deal about ham radios. I would like to connect an inexpensive scope to my shack but would like to use it to tune up my AL811H much like in another video using a Kenwood sm220. Would that be possible? Thanks again for your time and expertise putting out these great videos. 73 - W0KRD

[@andrewverran6998]

Great video , this unused port that is being used to sniff the RF , would this still work for a 15-20w cb radio ssb signal or would the outputting power be too low ? Cheers Alan. 😊

[@w2aew]

It will work fine!

[@spiderjuice9874]

Hi Alan, not sure if you check these older videos for comments, but I picked this one as I see you have the same model here as I do: I recently picked up my 2445B and am very impressed with it so far. However, the real reason I'm writing is to comment on your very extensive range of analogue (and digital) scopes - you seem to have a never-ending supply of differing models; besides the 2445B featured here, I have noticed also a 2467 and a 2465A CT (no doubt you have many more than just theses 3 models). I was wondering: could you do a video on what each of these scopes brings to the table for you, their unique characteristics, etc? I know from Dave Jones on the EEVBlog that the 2225 is special as it can display down to 500uV/div (I guess you have one of these too, but I haven't seen it yet for sure). What are some of the features of the other models you have to make them special in your workshop? Perhaps you could do the same rundown for your collection of digital scopes too. That is unless you've already done this and I've yet to come across it. PS. Hope your ankle is fully better now!

[@w2aew]

Great question. I certainly do have more scopes than any one person should! I have reasons for keeping each on around, although some of them are personal reasons rather than technical ones (is it possible to be sentimental about a scope?). It would probably make a good video though.

[@spiderjuice9874]

Definitely it's possible to be sentimental: I have a Tektronix 2225 on order, which will make 5 scopes all up - I am a beginner and barely know what I'm doing (if I knew any more, I'd be dangerous!), so 5 is certainly overkill and cannot be justified by any rational means. I will try really hard to stop here! Camera lenses were a problem previously...

[@cwebs1000]

How about just adding a BNC connector with just a short stub connected to nothing.

[@TonyButchT]

Great idea and very useful! Would you consider a video on how to read the displayed voice signals, in order to properly set microphone gain / compression? ( I use my rig's ALC meter, but leaves me wondering about what's really going on! ) Is there any chance an Eico 350 wide band scope can be used? Thank You!

[@luccamiguel6738]

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[@scotthank806]

@Lucca Miguel instablaster :)

[@luccamiguel6738]

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[@luccamiguel6738]

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[@scotthank806]

@Lucca Miguel happy to help :)

[@kschildt1]

For use sampling the HF frequencies, what are the minimum specs for an oscilloscope? Can any of the inexpensive USB scopes suffice?

[@w2aew]

Probably not - the scope will have to have analog BW that is at least close to the RF frequency you want to monitor.

[@G0HZU]

Your videos are always excellent and well presented but I'm not so keen on this sampling method because of the risk of damage. I know you warned about this more than once but I think it's a bad method to advertise to others because it is so vague and tuner specific. Your other RF sampler videos use much better defined and safer methods. RF damage to test equipment is always a worry and I use various methods to minimise risk such as diode limiters and even RF fuses inline with the limiter.

[@TheFlyre]

Hey brother - I need help, 🙏💯 I got my unit called " ENI PS 600" I Don't know what software to use?

[@volcanowb]

Thanks! Very much appreciated!

[@Mr.Amplifier.]

Hi there! If we decide to operate with limit power “1500 watts” can that be affected by creating high level of RF into the scope. Can the scope be damage?

[@w2aew]

Most likely not if your using this "stray pickup" technique. You may simply have to increase the v/div setting on the scope appropriately.

[@stargazer7644]

I think I would just mount a bnc on the back of the tuner and tie an unterminated sampling wire inside near the RF lines. Yeah, I know, the point was to make it simple. Well, this is so simple someone (you or someone else) is guaranteed to blow that scope eventually.

[@w2aew]

Certainly a bit more fail-safe - I like it. The "sampling wire" would likely not even have to be close to an RF line - there'll be enough RF inside the enclosure that a simple stub or small coil of wire will be sufficient.

[@Backtothefutureradios]

Do you think an unused port of an antenna switch would work? Thanks Larry…WA4PJP

[@w2aew]

Possibly. There will likely be a lot more attenuation, depending on the frequency, the power, and the switch. Worth a try.

[@Backtothefutureradios]

@@w2aew Thanks!!

[@felixcat4346]

If you used a 100 watt light bulb for a dummy load would the bulb flicker to the tune of the signal or would it just glow at a steady rate.

[@w2aew]

+Joseph Nicholas It depends on the modulation type, and the bulb. Not the best idea these days, since the impedance of the bulb is not consistent (differs with brightness), and not a perfect match to 50 ohms.

[@zoolkhan]

also it radiates. the idea of a dummy load is low emissions. a light bulb is not low emissions.

[@MarkTillotson]

Put the bulb in a metal box!

[@Satchmoeddie]

I have that same scope! I have a Tek with a huge screen and want to make it into a station monitor. One channel is dead, but I have good horiz & vert on the other. I paid $30 + $20 for shipping and got $200 in probes so, the scope is a freebie.

[@Satchmoeddie]

You mean my 2245B won't handle 1500 watts? LOL! I have the big huge differential probes and transformer that will handle over 100KV. I want to use little student grade scope I bought, not the 2245. 73 KI7AQJ

[@SITIMPE]

Hello. Thanks for the video. I transmit am signals from raspberry 3. The max output power is 200mW. Can I plug it directly to my scope? Or I need rf sampler? Thanks.

[@w2aew]

That's about 9Vpp into 50 ohms, so as long as you can set your scope to a few V/div, you should be ok.

[@SITIMPE]

Thanks for the answer. The input has 1MΩ impedance. Is it necessary to buy 50Ω impedance adapter?

[@w2aew]

It would be a good idea to use a 50 ohm through terminator.

[@ZeroLabsLive]

Hey, I've got a 2445 too but it has a problem. The Li-ion backup battery won't keep a charge. It's 3.6v. For a quick test I tried CR2032 and it drained very quickly. I've also replaced it with the exact part for about $30 and still no joy. The symptom is it requires that I acknowledge the error every time I switch it on, it will not hold settings and the bottom line of the display fills with "?????2v???????????1mS????????????". Ever run into this?

[@w2aew]

+Zero Labs Live I haven't, but I have heard that some versions of these scopes have RAM chips that go bad. Also, some versions have supply caps that go bad. If you have caps that have gone leaky or partially shorted, that would explain the battery draining quickly. I'm not sure if bad NVRAM chips would cause the problem you're seeing. I would suggest you post a question on the Tekscopes group on Yahoo - or simply search their archives, there will likely be an answer there.

[@ZeroLabsLive]

***** Thanks. I've just applied for group membership so I can search there. Also found some good posts by you and others over at Dave Jones forum EEVBlog. Love that guy! :)

[@carstars]

Interesting. I think I would put my real outputs as 1 and 2. Without switching by the scope. Thanks I think I will try this or something similar soon.

[@w2aew]

Good idea - helps to reduce the possibility of transmitting directly into the scope.

[@bradleyhewell784]

Couldn't you just install a BNC into the back of the radio with a dead short near the RF output and have the same effect?

[@w2aew]

Probably not - the RF is pretty well contained/shielded inside the radio.

[@902Steeler]

Would this work with an antenna switch box as well? It should in theory

[@w2aew]

Yes it should - how much coupling you get will depend upon how well the unused ports are shielded from the active port.

[@902Steeler]

@@w2aew thank you!

[@gadget73]

Another cheater way to do this is to take a few turns of wire around the coax feed to the antenna.

[@zoolkhan]

thats how i do it

[@АндрейДенисюк-ш7п]

Bad news for you. You have common mode current on you coax and rf in the shack )))

[@TheH3nrydesign]

👍

[@jma8352]

but then you got to buy more expensive equiptment

[@deconn1948]

That neat ng9p

[@terrya450]

You should be sampling off of a dummy load and not going directly into your scope

[@w2aew]

In this example, I use a dummy load on ANT1 and transmit into that. The scope is connected to one of the unused ANT ports. I make a point in the video at 2:45 that you do NOT want to connect the transmitter directly to the port that is connected to the scope. The scope is connected to an UNUSED antenna port, which is acting as a near-field sensing probe inside the tuner - no direct connection to the transmitter.

[@olegtf]

Absolutely useless for any practical purpose.

[@imken2392]

I'd like to display a trapezoid on my Tektronix 2465 BDM scope. I've got the sampler and de modulator but can't see where I input the X and Y in ch 1 and 2 to get the vertical and horizontal display for modulation and carrier. Please, help...???

[@imken2392]

Never mind, I found it on the SEC/DIV rotary switch.