Відео

Great video, particularly because you highlight the two active frequencies either side of the carrier. I am struggling to understand this. Are these + and - of the same tone frequency, or duplicate single frequencies? I believe AM creates duplicate side-bands so you can listen to one or the other. Also, in FM bandwidth I assumed the low tone frequencies would be lower than the carrier and high frequencies higher, but the examples I've seen also form a peak at the carrier with what appears to be mirrored signals either side of it. Please excuse long, dumb question.

Can a carbon fiber pole be used to mount the MLA-30 antenna?

This is very good -- though it's quite obvious that the return loss (SWR) curve changes only when the objects are VERY close, and practically touching. Even a few inches seems to avoid a severe detuning (and presumably decoupling). It's not very clear to me what the likely impact is from a received signal strength perspective, for both incoming and outgoing signals, as long as the conductive materials are not essentially touching.

So short sections of carbon fiber golf club shafts used as spacers for home built ladder line with insulated wire or folded dipole element separators with insulated wires SHOULD be benign? Or would it add large capacitance? Surely it would not re-radiate HF since only a few inches long and perpendicular, right?

Any idea how to speed up that recovery from strong signals ? It is too slow for me.

This is a simulation? And yet, this doesnt factor in that the feed point is not at the base of the J? In fact, the feed point should make the impedance zero at the base of the jpole, so anything below should not be radiating at all.

Damn, I really need to get that wooden walking stick. It significantly improves the antenna and acts like a Q muliplier.

this is cactus, not j

It seems like the two important points from the video regarding the effects are that: 1. The assumption is that the mast material and the antenna are parallel. 2. The mast is in very close proximity to the antenna. So, what happens if the antenna on atop the mast instead of hanging parallel to it?

Sorry, I think this is wrong. DC ground and RF ground are completely different. The j-pole transmission section will be lowest resistance at the frequency it is designed for, and the mast will appear as a high resistance at radio frequency. In any case, the coax of the feed must be grounded before it enters your shack for safety and noise reasons, no? That ground is attached to your antenna and a jpole has a short in it. Same thing.

Great test but possibly only valid for that style of antenna? A random wire or EFHW in one of the HF bands running straight up the pole would be a good test to run too.

Great testing method. Very nicely done.

Maybe you should've worn insulating gloves when conducting your tests

If larger bandwidth is better, why would anyone want a smaller bandwidth? Does it save battery or energy? Does it reach farther? What are the benefits of having smaller bandwidth?

Woodbridge va here, going to take some tests later today. Thanks for the video.

Very good video. I am making a video right now where I have to explain bandwidth to a layman. This is hard to do without visuals like you have shown, you did a great job explaining it.

Wow thank you so much for this video, your video. I have an old Kenwood ham radio that I'm experimenting with am bandwidth. It is around 10 khz and now I know how it really sounds. It's am broadcast quality not bad for a poor boy.

Lame. Do a voiceover, do an article. Don't make me read your video

if i ground it i lose signal

@5:23 is that a TM-D710G? Did you bring it for APRS? Might also be nice for dual band and voice alert. I usually setup a beacon when I POTA, havent caught any QSOs strictly from it though. Hopefully when I start SOTA (this afternoon W1/CR-006) it will help out a bit better. Either way, its kinda neat to see your path on APRS.fi and see who is out there. I will be using an N9taxlabs slimjim so similar setup antenna wise. Nice helpful video without being several hours long. Just enough motiviation and explanation to get us out there. 73 - KC1OCA

Thank you for a clear, concise comparison of the two methods. I've been playing with Ansoft HFSS which works more along the lines of FDTD technique, but it also requires longer run-times than MOM like used in 4NEC2.

Useful content. So is your conclusion your final antler?

New subscriber here. Thanks for the video. I am new to ham radio and considering what sort of mast to use (mainly for portable use). I wonder how far away the antenna can be from a conductive surface like the carbon fiber pole or a metal tower where it would not de tune the antenna.

Does your receiver still operating

Dude, this video was awesome. Helped me explain bandwidth to my wife in record time.

If we use a carbon fiber mast in the usual expected fashion, we attach a vertical antenna at the TOP of the mast. The antenna is far away from the carbon fiber pole. The antenna is NOT lying parallel and/or adjacent to the carbon fiber pole. Could you please repeat the experiment with the antenna attached at the TOP of the carbon fiber pole and see what results you get? That would be the truly relevant test. Thanks for your great work.

That was very informative!

A conductive mast becomes part of the radiating element. I just proved this with my 70cm two bay J-pole collinear. I got it to tune-up by itself but it changed after lifting it aloft on a metal mast. Yes, I grounded it. I used a Nano VNA with a wide frequency sweep and observed a comb family of SWR notches in a "V" going both higher and lower from the design frequency. These notches moved around while sliding my hand along the mast. To solve this, I installed a pair of back to back pipe fitting transitions, solder to thread, and isolated with a very short threaded PVC section, right under the "T" fitting. Problem solved! Grounded or not still has this problem as there will be standing wave reflections from either a short or open. As reported below, if you are determined to have a DC path, then a quarter wave "hairpin" stub at the isolator might work. A mast is usually cut to an arbitrary length and it's the luck of the draw if it is resonant at the design frequency. This can explain why some people have good results while others not.

Nice test! I wonder what effect carbon fiber would have HF frequencies ?

Very cool cat✌

when it starts, i thought you gonna rap😂

Junk science.... at its worst.... waste of our time... What happens when a ham operator thinks he knows all about testing antennas...

I've been reading your logs and experiments at hamradio.me for two years now and love your content. Having a bit of electronics and physics education myself, I appreciate your thorough testing methodology and explanations of your findings. It amazes me how so many people still think J's don't need a choke, or the bottom T stud doesn't matter. I think that shows too many are too absorbed into HF and the big antennas to care about VHF/UHF operation and just accept whatever they were told. Those same people are amazed when I tell them I can reach repeaters 60 miles away on 1W of 440 MHz from inside my house, using a simple 20AWG loop antenna, tuned with the help of what I learned from your site. Thanks!

Very good test. Thank you for doing this experiment and sharing the data. You should send this data to Gigaparts re: their 34 foot carbon fiber multi-section mast product.

Maybe a dumb question: but would wrappings the carbon fiber mast with insulation tape do anything?

Thanks for taking the time to test this. Learned this long ago but I never have tested it.

Awesome video! Experiments like this are needed!

Very cool Alan - seems definitive! Thanks for sharing.

Thanks for the video - very helpful! I have a SOTABeams Carbon6 which I plan on using for an inverted V random wire end fed antenna, so I’m glad to hear that the mast will work fine in this configuration. Your video was invaluable to ensure that I don’t try to use it in a vertically polarized configuration. Great work! 73, Mark K0EHR

Hello, thank you so much for the information and the experience. I have a question for you as an expert, I want to use a mast to used for mounting cellular signal booster antenna weboost , also for mounting some wifi antenna from Ubiquiti. Is the carbon fiber will effect negatively on the performance of the antenna devices? Thank you

So how should you install a j pole. I am getting my technician license soon and am eating to set up a small base station with a j pole... Now I'm confused??? I was going to use a old DTV dish mast but now am thinking not the best way to go.. any help will be awesome thanks..

Great video. This is the most conclusive evidence I've seen of the impact a carbon fiber pole has on an antenna. When the weather warms, I want to do similar testing on my sloped antennas.

Antenna seemed to have worked great.

You sir, are owed another antenna for the go bag etc...Contact me on eBay. If you would like, just tell me to make it with the sma male for your Yaesu for a direct fit. Thank you for this very fair and detailed review. Great time you had!

Good Job!

Are you available to design 2 co-phase 2 element Delta loop wire beams for under my 16’ tall bay house on stilts? I need modeling done before I build. If interested, contact me via my UA-cam channel contact. I will pay you of coarse for your time. 73’s George

First, one v-can not see the details of the software t-because of the bad quality video. For what I can see is that yoy have not calibrated the RSPduo to show the exact signal figures. The miniwhip is of a minor quality and has to be mounted about 5 meters above ground to work good. Also comparing these antennas is like comparing apples to lemons. From the ORIGINAL miniwhip by Roelof Bakker PA0RDT has re-designed a EcoWhip wich can be used to feed over the coax from the Bias-T of the RSPduo. I have used different MiniWhip models over the last 15 years and almost all are poor performers wit a high base noise. You can always send me a PM for more info if you wish. Why not use a balanced open dipole with a ladder line for the Hi-impedance input instead of a wire. Its more quiet and its extremely cheap and easy to make. Good luck!

Great demo of the RSPduo using SDR Console and the usefulness of the high impedance antenna port. By the way if you use SDRuno there are a couple of extra neat features. One is the ability to simultaneously view both tuner inputs simultaneously (Dual Tuner mode). There's an example here (8 minutes 40 seconds in): ua-cam.com/video/91fCXPQnlTc/v-deo.html The second extra advantage of SDRuno is that the power readings in dBm are calibrated to within +/-1dBm accuracy for the 50 Ohm inputs which may also prove useful for absolute signal strength measurement. Regarding direction finding with the RSPduo, we are still working on the software for that.

What about static buildup? It doesn't take much charge to fry electronics. If the j-pole is mounted on a plastic mast, can I still ground the antenna cable at the other end?

what about lightening?