I've finally found some time to use the early VNA which I bought in the Covid lockdown period... and this set of videos is so useful, thank-you! I hadn't thought of using the VNA in conjunction with my antenna matcher but I will now. What a great idea! 👍👍
I have been using an end fed random wire antenna for years with great results. The unun is grounded to a steel window well and I also use a choke on the coax just before it enters the shack. The choke is key since it prevents RF from entering the shack
Thanks for doing this video. I’ve got the same ATU and will be doing the same when my VNA arrives - EFHW is how I usually operate portable so this will make short work of setting the dials for different bands when in the field!
Transmatch + NanoVNA + 5 minutes of knob fiddling = Autotuner. 😀 Kidding aside, it was great to see how all of this works. Much more educational than pushing the TUNE button. Thanks for these NanoVNA videos.
Steve Ellington has some excellent videos on testing and optimizing EFHW antennas. The short and skinny is: 1) inverted-L, 2) balun fairly close to ground, 3) good earthground at balun, 4) choke the crap out of balun at the feedpoint, and 5) no counterpoise. That should provide a little bit better than 3dB improvement over most installions. It will turn a so-so performer into a good performer. Also, usually "A tap" is the full inductor. A general rule for best performance is minimum inductor with high capacitance. It provides the highest Q tuning.
A 49-1 UNUN is what you need, not a BALUN. And I think that this is the first VNA video I've seen that is checking an antenna other than a 2 meter or 70 cm. Thanks
@@davep6977 the air core you are talking are not really efficient, see this page www.karinya.net/g3txq/chokes/ and take a look at this wonderful video of trx bench, now that is a real effective choke that cover all amateur bands and it is quite cheap to build too : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-JhAPJISUjB8.html (sorry to plug another youtuber video on someone else page) but I sincerly think it is a great demonstration on how common mode choke work and how to build a really effective one.
You cannot just go up or down in a vertical straight line on a smith chart. When you add or remove reactance with capacitors and inductors, you also move left or right. The shortest and ONLY path toward the center of the smith chart is therefore a combination of two curves. For instance, you must go enough left with the capacitor in such fashion that when you finally add inductance, you curve right, back to the center of the chart. See ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Hsx4wqAlqlQ.html It's easy to explain visually than in words.
Nice video thinking of buying on and looking for a review. You need an unun on an end-fed not a balun. A centre-fed antenna is balanced while coax is unbalanced so a balun, balanced to unbalanced. An end-fed is an unbalanced antenna, so unun.
in order to take these measurements, you did need to calibrate the device at the end of the tiny peace of coax ? if so, you probably did need to have sma to pl259 adapter, this means the calibration is again wrong because of the adapter ? your you need a calibration set for sma m/f, another one for N m/f and another one for pl259/so239 ??
I'm no expert at this but I do the calibration with everything but the antenna connected to the VNA, if possbile. But I only have the SMA version of the S. O. L. T . so it is just to the end of the tiny coax. Maybe that is good enough??
the radio is disconnected and the VNA takes it's place. you wan to radio to see 50 ohms so if the VNA sees 50ohms then you put the radio back in.. same as an antenna analyzer. The VNA outputs RF (weak transmit) and measures the reflected signal for amplitude and phase.
I wonder if the Nano VNA could be used to tune I F strips in a radio, I have used a sweep generator , also a Wobbulator , and my spectrum analyser, I've just bought a Nanovna impressive little tool
Question. I have a dual antenna whip nagoya. It has 3.5vhf and 5.5 of gain uhf. If i tune the uhf frequencie tona desire, will the gain dimish or be affected and the vhf .
Been a Ham since the 1970's extra class WAS WAC DXCC. I had an offset dipole on a 4:1 balun that I set band SWR using my HP8921a. Worked great. I though an end fed would fit my yard better. first time using a 9:1 unun. I've got a good ground on the balun. the ground in the garage is not great. although the 4:1 balun system was working fine. I suppose an RF choke would help things. never had to use one before in all my antennas over the years. different data on wound toroids and multi small cores over the coax. I think I will go back to the windom type
I think I found the problem. bad ground connection to the transmatch. I only added it recently. A flea market find. even without an RF choke things are acting normal.
@@IMSAIGuy That's great! I really like Endfed. I do a lot of QRP and live in an HOA restricted area so its end feds for me. I find them easy to put up and tune. I have mine as an inverted L in the attic. Hope to hear you in the air. 73, KF7ZVL. What does IMSAI stand for?
Here is a more basic introduction for newbies that shows the menu options visibly clear: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-QJYeFpiqY8c.html This video assumes you already are familiar with the menu.
