You don't have to spend much time on the air or visit many ham radio message boards to hear of people who have experienced blown finals. In this video, I'll tell you how to minimize the chance of this happening to you.
Very good advice about always metering SWR rather than RF when on the air. I've forced antennas that were 'way out of natural resonance into a 1:1 match with my antenna and ground tuners, and then seen SWR climb dangerously during operation due to the balun in the AT getting saturated. If I hadn't been monitoring SWR regularly during TX, that would have fried my rig. Also good advice about paying attention to feed lines and connectors. The first thing to do whenever you detect unusual SWR or RF out levels is go around and reseat (unscrew and re-screw) all coax connectors. Cheap jumpers in particular are susceptible to seat imperfectly (but you can't feel that with your fingers) and mess up your game. Thanks for the great video!
Tracy, You are right on. As a ham for over 50 years I still needed to be reminded of many of the things that you discussed. Even at QRP levels it's easy to blow the finals in a FT 817 or other QRP rig when the antenna isn't matched. Dave K8WPE
I use a homebrew resistive SWR meter when tuning aerials. The rig never sees more than a 2:1 SWR (100Ω maximum) but allows all SWR readings to be read, it does need to be taken out of circuit after tuning because it introduces attenuation. I always have the FT817ND indicator switched to SWR. Good advice to disconnect the aerial when not in use. I always have. Years ago I saw sparks jumping across 2 inches from my wire aerial to the wall from statically charged rain. Bill, G4GHB.
Good video. Those coaxes can have a break in them as well. Back in 2012 I was back Hom in Santa Rita NM and Set up in an RV. I had a coax going to an MP1 antenna. little did I know that there was a break somewhere in the coax and it cost some repairs later on. Finals and capacitor had to be changed out. I now always take a meter to test if I'm doing portable as well. That day it cost me contact with Lastmans standing setup which I was looking forward to.
Hi all...With using a Manual antenna tunner , I Prefer to Tune first for Best Receive and then set the FWD Calibration quickly and then switch to REF .......> always remember on unknown antennas ...best to transmit a very brief and quick TX...to Calibrate the meter ........73
Is there any advantage to tuning up using the minimum output power a rig will put out while adjusting for swr and then increasing the output power as needed? Very clear and useful information. I always unplug everything now after having suffered a lightening strike. I had the antennas disconnected but not the commercial power. Lost the whole station. A very expensive lesson for sure.
Absolutely there is, Tom. Reducing power while tuning is best practice as you will expose your power amplifier to as little danger of high reflected power as possible during the process. Very sorry to hear about your misfortune.
Thanks for such an informative video. As usual very straightforward and simple. Clear and precise. By the way watta Gorgeous Old Icom you have back there wooooow neat and clean. Shine and pristine. Being a collector I enjoy watch this gems in such a wonderful conditions. Would be nice watch them in action. 73s de KK4NWW
Thank you, Eduardo! The Icom IC-740 is a very nice old rig and if you watch the used market carefully, you can pick a good one up for an extremely reasonable price. The sad truth is, today's ops don't want rigs like this any more.
I didn't hear you mention properly grounding your station. Excessive static should be brought in on the shielding and discharged to ground if coax is left connected.
Hi Tracy. Catching up on your videos (great stuff as usual - you've taught me so much)! After watching this video I have a question for my "On-Line Elmer"! Concerning auto-tuners for my FT 817-ND: I use an LDG 817 Z auto-tuner for my 817 and was wondering if a max of 5 watts is going to make a difference and pose a threat to my radio. It seems that higher wattage going back into the machine would be worrisome, but is it going to make a difference at 5 watts? I've used the LDG auto-tuner for my SOTA work and other Amateur activities for about a year now and it seems to be efficient and safe... Now, you have me thinking... "Hmmm... I wonder if I'm going to hurt my favorite radio!" Could you give me some insight on this? (BTW: Since I've last talked with you I've installed the bhi DSP board and, WOW! My little 817 went from great and fun to Super Great and Super Fun!) Thank You For All The Help! 73! David, K7GYB PS: I've only used the PackTenna (@92ft. w/9:1 transformer) for the 817 in the field as I now have a base-station radio (IC-706 and use a manual antenna tuner for it). DV
Hi David, thank you for the kind words! You raise a good question. The final transistors in QRP rigs have a much smaller power rating than those found in 100 watt rigs, therefore they are just as susceptible to damage due from a poor SWR. You really need to be careful with the 817 due to this. Congratulations on the BHI filter, I've heard nothing but good things about them. Have fun with your 706, I used to own a 706 MK IIG a number of years ago and really liked it. 73 my friend!
OK... Thank You. I think it is time to look for that little Kenwood manual tuner like you have or something similar. Thanks again for your sage advice. David K7GYB.
And always use a separate ground system for your radio equipment. If you use the grounding system of your house, where all the other appliances are connected to, RFI will find its way into the RX.
