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 11 
 on: Yesterday at 09:10:22 PM 
Started by KB1WSY - Last post by KB1WSY
Spent much of day rewiring the detector: changing the capacitor values in the tuned circuit and rewinding the tank coil to try to get Peter/G3RZP's suggested 10µH/50pF LC ratio for the 40m band. (Haven't yet built the RF stage; decided to alter the detector stage first.)

Am rather discouraged. With antenna connected in the usual way, receiver is overloading drastically on almost every signal. Altering value of the series capacitor in the antenna connection doesn't help. Also, regeneration control is noticeably rougher and very "touchy" (I tried changing the tickler's turns and position, but it didn't help). Just much worse all around.

Tomorrow I will probably experiment with the tank-coil form factor. As of now, it is 15 turns that are 0.7" high, wound on a 1.25" pill bottle. That is nowhere near the 1:1 height/diameter ratio that Peter suggested for maximum Q. Looks like I should try a 1" or 3/4" form. On the other hand, the current symptoms (serious overloading) imply, don't they, that the Q has *increased* compared to the previous LC combination? Won't even higher Q make it even worse?

Another thing that's puzzling is that my calculations for number of turns was way off. To get 10µH it should have been 18 turns, not 15 (15 turns is supposed to be more like 7µH) and yet the only way I can bring in the desired band (6950-7150) is with the 15 turns (I don't have an inductance meter). I've done the calculations for the capacitance network over and over again, and believe them to be correct.

Edited to add: I've just measured the frequency coverage from one end of the dial to the other and it's only about 140kHz when it's supposed to be at least 200kHz. That tells me there's probably something screwy about the capacitor network (and also that the 15-turn coil is probably closer to 7µH than 10µH). It's time to go to bed -- I will check my wiring and calculations again tomorrow!!

The coil is also extremely fiddly: very small changes in the spacing of the windings yield very large changes in the resonant frequency of the tuned circuit.

As I understand it, Peter's rationale for the change in the LC parameters is to provide a better load/impedance match when the RF stage is added. My question therefore is: Should I worry about the sharp deterioration in the detector, as a stand-alone detector? Is everything going to be OK when the added load of the RF plate coupler winding and RF stage is added, will it just dampen all that overloading?

73 de Martin, KB1WSY

 12 
 on: Yesterday at 08:31:55 PM 
Started by AF5CC - Last post by VK3MEG
Quote
THIS.

And I wouldn't even say "giant." My C31XR was a miracle worker at the bottom of the last cycle. Although I couldn't really make propagation on 10 with it, I heard stuff on 15 and 20 that few others were able to copy; and certainly not with verticals, wires and other inefficient antennas at 30 feet.

Furthermore, the difference between 50' and 70' is absolutely huge on 15 and 20. When I drop my tower during windy conditions I find WWV signals and NCDXF beacons that are usually strong are barely audible on the same antennas just 20 or 25 feet lower than their usual spots all the way up. Height matters and gain matters. You don't need to be a contest super-station on a mountaintop to do it--just a good tower and decent Yagis.

been having this debate i'm in your court  W2IRT  height is might in this game th best i can do is 30odd feet and i'm glad i have it but the differnce is huge if you are higher. Luke vk3hj has a similar antenna setup but only 4 compared to my previous 5 elements but at 60 feet he hears stuff i cant dream of hearing. i then went back to 3 elements and its scary i dont hear half of what i was hearing and my report are s2 points down. give me height over gain any day of the week till abut 75' i feel from my research thats the optimum height on flat land for a dx'er not a contester.In my part of the world.


 13 
 on: Yesterday at 08:26:19 PM 
Started by KK4AXX - Last post by KB4QAA
In one discussion several years ago about coax feedlines in the shack one engineer suggested 50k Ohm 1 or 2 watts across the coax.  Another who designed industrial radio devices said he puts 25K Ohm resistors at the input side of his radios designs.

 14 
 on: Yesterday at 08:12:00 PM 
Started by WO7R - Last post by NU1O
Quote
I don't think one person should be in control of a DXCC entity.

I have sympathy for this argument, but it would need to be carefully developed.

I can think of several DXCCs that are effectively controlled by a single operator right now:  5T, 3C, 3C0.  Making that argument naively, all look to me to more-or-less qualify under the "single operator" standard.  I can't make the case for deleting them, though, so the "obvious' rulemaking is out.


I haven't heard of Jean, 5T0JL, blocking other hams from getting a license to operate from Mauritania.  A Polish team went there in late 2012. 

I don't know who you're referring to with respect to 3C and 3C0. 

73,

Chris  NU1O


 15 
 on: Yesterday at 07:52:02 PM 
Started by HS0ZIB - Last post by KF7VXA
If there other Hams on the island, you could set up a pre determined emergency frequency using H.F. NVIS antennas and possibly get reports from different parts of the island and also VHF/UHF communications. Between ground wave and sky wave, you should be able to cover most of the island with H.F and VHF/UHF.
You would need to set this up in advance.
If allowed by your radio laws, maybe set up an Ares type net that meets weekly.
This would enable you to give better reports to the outside world as well as get help where it is needed the most.
Not knowing the size of the island, population centers and number of other hams, this would be something you could look into.
I hope those type of emergency communications are never needed.

John

 16 
 on: Yesterday at 07:41:43 PM 
Started by HS0ZIB - Last post by K5TED
With Mark taking the coveted 'Turd In The Punchbowl' award, I'd say anyone able to get a status report out to the world when disaster strikes anywhere but sunny New Mexico, the Maritime Mobile Net or Pacific Net would be first choice for reporting in. Those nets are all day and usually have connections with big stations who can at least take early status reports and pass them to some authority. Who knows the value of an early report? Probably depends on who benefits from it. Surely can't be be predetermined by someone in an airconditioned shack 7000 miles away... Might as well try to help rather than bow out under fear of irrelevance.

 17 
 on: Yesterday at 07:16:20 PM 
Started by K1YTG - Last post by K4DPK
Hey Peter

Question:

Given the low gain and sensitivity of the tube being used (TL), if he used a 200 ohm non-inductive resistor from grid to RF ground and drove the stage through a 4:1 transformer, wouldn't this greatly simplify the neutralization?  

Of course, it would still require considerable drive, but it shouldn't be as squirrelly.

Phil C. Sr.
k4dpk  1955

 18 
 on: Yesterday at 07:11:53 PM 
Started by WO7R - Last post by VK3HJ
Chris I understand what your saying but Monk Apollo does work his fair share of pileups every year.  Almost Every ham has a better chance of a contact with him than they do with most of the others in the top 50 most wanted.

I must disagree.

If Apollo worked "his fair share of pileups" he wouldn't be Most Wanted #4 in Oceania. I have worked around 27 of the current 50 Most Wanted in ClubLog's list in the past several years, and Mt Athos is still not one of them. Several of those wanted entities are to be activated by proper DXpeditions next southern summertime.

Europe is NOT hard to work from VK. I can do it EVERY DAY.

73,
Luke VK3HJ

 19 
 on: Yesterday at 07:11:33 PM 
Started by KK4AXX - Last post by WB6BYU
What is the impedance at the point where you plan to install it?

How much power do you plan to run???

 20 
 on: Yesterday at 07:02:56 PM 
Started by K1ZJH - Last post by K0UA
I still have an old Navy flameproof I use on SKN and sometimes just for fun, especially if replying to a slow sender.  But I mostly use my Bencher paddles, when I am not using a microphone Smiley  or other digital mode.

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