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Hello Bill,
There are many possibilities that could cause the SWR to be high on several bands. A sketch of the antenna design including the antenna wire and feed lines with their rough dimensions would help nail down a solution.
It is possible the antenna itself is a low impedance (Z) on 40m and the coax is around 1/4 wave (or odd multiples of a 1/4 wave) long which would transform the ant’s low Z to a High Z at the tuner. It can also go the other way where the antenna is high Z on 40m and the coax can transform it to a very low Z. I suspect something in between these possibilities. One quick test is to insert a length of cable between the antenna and the tuner. For 40m I would try 25′ if it is available, if not use what is handy.
Performance on 15m and 40m are often related due to their 3:1 frequency difference. For example 1/4 wave long on 15m is 3/4 wave long on 40m. 3/4 and 1/4 have the same affect…
Another factor is the actual Z at the tuner. The 939 is a L tuner with a series inductor and a shunt capacitor making the shape of an L. There are impedance values that cannot be tuned with this combination. While the 939 can place the shunt C before or after the inductor giving it the capability to tune a wider range of impedances, it still doesn’t cover the full range of possibilities. Once again a length of cable between the antenna and the tuner might transform the Impedance to something the 939 can tune.
I would also test the affect of removing the choke on the shack end of the feedline. The choke could make the shack end of the feed-line appear to be high Z which when rotated back down a 3rd of a wavelength (50′ on 40m) to the tuner it may affect the tuner’s anility to tune.
There may be issues with how the feedline is routed to the feed point on the mast. A sketch would help.
It’s nice you got a flagpole up. Have you been chasing the 13 Colonies special event stations?
Hamilton K1HMS
The FT-450D lives again.
Many radios have a internal GDT (gas discharge tube) right at the RF connector, this radio has it located after two relays, the bias tee inductor, a parallel pair of series capacitors and connected with using a via hole.
The first relay had significant melting and char marks, a PCB trace was missing to the bias tee inductor, one of the series caps was 1/4 gone and the other cap’s metal end terminations were all that were left on the board.
The image is the PA board with the SO-239, relays, and L5403 inductor removed. The PCB trace no longer extends to the hole used to mount the inductor and there is some board charing left after a thorough cleaning. The white GDT (D5409) is still on the board.
[attachment file=”85484″]
I wonder about the engineering process that lead to a GDT rated for 2000 amps being placed after a string of components rated for 1 or 2 amps and connected through a small via hole.
There were a few penny parts (diodes, transistors, regulator) that were damaged and replaced. Most of these were on the bias tee line after the inductor.
Unfortunately the blown regulator took the MCU IC with it. The radio is using a processor board from a 450AT that was upgraded to a 450D while we attempt to locate a replacement MCU IC.
The RF/IF deck, DSP, synthesizers, RF drivers and Final MOSFETS, and the front panel and its processor, all survived without a mark and perform perfectly.
I have seen several radios that took an antenna strike. Those, like this one, with a ground rod and a Polyphaser or other quality surge protection had similar damage and were easily repairable even when the antenna, balun, and coax were reduced to charcoal bits in the garden.
The radios without similar protection were damaged beyond repair….
Hello Scott,
My first HF radio was a FT-450D. It was a eBay “for repair – it worked when I turned it off and never came back on.” I thought “how bad can that be” and bought it.
It was clearly a lightning strike. Nearly every device on the DC circuit was dead, ICs had cracks, and tiny devices like diodes and small MOSFEET switches were missing replaced by a pile of black charcoal. There were over a dozen parts that needed replacing. The Digikey parts order came to $26. The 450D lives.
I have since repaired a number of lightning struck rigs. Many require $10 in parts. A few have needed a new processor board ($168) and new finals ($175). Only one was beyond repair. A service center will add labor and there is also shipping costs which can push the cost beyond the value of the radio.
If you are interested I can take a look at it. You’ll need to leave it on the door step, we can have a zoom session to go through it and also talk about grounding.
Congratulation to the CRHS team and to Fred for another successful ISS contact!
I was able to copy the ISS downlink with an HT and a mag mount 1/4 wave vertical whip on top of my car. Due to the west to east track, I could not copy the beginning of the Contact but after that, it was 7 degrees above the local horizon it was a clear strong signal to the end of the contact.The questions Dr. Drew Morgan answered were interesting, I especially liked the one concerning blood flow and distribution in zero gravity.
Progress, I have wsjt-x running on the RPI-4.
Now, I’m looking for a Raspbian 10 Buster compatible Logging program.
Hello Bill,
Welcome to NARS.
There are many in the club that can and will help, just post your questions or contact us directly. This is new territory for many and no question is too simple.
For /MM salt water is your friend. You may already have enough metal below the water line. Often the ground side of the antenna feed is capacitively coupled to prevent electrolysis.
“Net Logger” is a good resource to find open nets including the Maritime net out of ME. These nets like traffic so do not hesitate to check into the XYL, Navy, ME Potato, or other net.
I missed seeing this earlier. There are a couple of places near Manchester I recommend.
The first one is ESS. It has a wide range of components, assembly tools, cables, case fans, project boxes and much more. It also has used test equipment and some military surplus.
It can be found at http://www.esssurplus.com/
ESS
900 Candia Road
Manchester, NH 03109
Phone: (603) 624-9600
Fax: (603) 624-9700
Hours: 9:30am – 5:30pm (EST) Mon-Sat
The second one is PAR Electronics at
250 Commercial Street # 904
Manchester, NH 03101
Phone: (603) 623-2009Once you find the building you go around back on the right side near the river and it is the first door on the rear by the loading dock. This place is packed, it is cavernous, and unbelievable. Peter does not have a web site and sells a lot on eBay. He has a very wide range of “electronics”. There are shelves to the high ceiling of test equipment of every type and vintage, microwave devices, used but nice METCAL soldering irons, cables and connectors of every type. If you need a WW2 X band radar pedestal with dish, or a 100 watt S-band TWTA you will likely find it there.
Wow, it is a surprisingly violent event. We see the average motion due to the burst which is pretty wild. I wonder what the peak impact is.
The initial acceleration as it falls and as the air density increases would be interesting and good science.
Maybe it is time to add a 3 axis accelerometer.
Hello Miguel,
Welcome to the forum.
The 818 will operate down to 9.6V so 12V shouldn’t be a problem. Also 2.5w is only 3.8 dB less than the full 6w. This is only about 1/2 a S unit at the receiving station.
QRP is always a challenge, that is part of the fun. From that location someone on 40m should hear you. I suspect the antenna may be an issue.
At QRP power levels the antenna becomes even more important. You should have a SWR less than 2:1, anything less than 1.6:1 would be great. Placement of the antenna is also important.
I’m not familar with the “super antenna”. What type of antenna is it and how high is it mounted?
When I operate QRP and call CQ I add QRP after my call sign. I find OMs are reluctant to work weak signals but like it when it is a QRP station. Also you are a IOTA.
<p style=”text-align: right;”>Monhegan should be better than Portland since the noise level is probably lower and you are transmitting over salt water with no obstructions.</p>
Now 10m is a real challenge, even with a beam and 100w.If you let me know a time and freq on 20m or 40m I’ll listen for you tomorrow. From 5PM to 9:30PM I will be QRT.