开云体育

...not sure I can be up at 0300...x'ing ma fingers there might be one left by 0530 (my time)

Cheers
Scott
JS6UEY

I've been using with success end fed antennas on 40 m and 20 m for portable operations with a FT-818. One end of the wire launched on a tree as high as possible (or suspended to the tip of a 10 m fishing pole), the other end in the vicinity of my RTX with 2 m of RG174.

To tune the antennas I have built a couple of those?. I made them from scratch with components bought in the local shop + ebay using a breadboard (not bought the kit), and put both in the same plastic box (roughly half a cigarette box size) with a switch to select the band. It works OK for me.
Made some tests with and without a counterpoise and didn't notice any difference, so I'm using without any counterpoise (although in principle there should be one, I think, probably it is the low power which makes the difference practically negligible).

I forgot to mention: If you build this, leave the diode leads long to help with cooling. Also consider using a capacitor at the output of the switch (as large a value as will fit in the enclosure, at least 470 uF) to smooth out the switching transients so the QDX won't power down then reset.

73
Andy
WM8Q

My problem was keeping the QDX output power low during antenna tuning.. I didn't want to expose either the external amplifier (when connected) or the QDX PA transistors (when "barefoot") to ridiculous SWR, either steady state or transient. I don't want to tune at 40 watts in any event, obviously bad practice.

Keep in mind that since the QDX always outputs the same (maximum) power, it slams the external amp to full power.... bad while tuning, when the SWR is very likely awful at times.

The answer was a 12-position rotary switch that selects taps along a chain of 11 diodes, each with a 0.67v forward drop. It's in a tiny box with powerpole connectors at each end. Easier to build than a constant-resistance stepped attenuator between the QDX and amp.

I now tune at ~9 volts, and run at 12 volts. Problem solved.

Another benefit of this variable supply add-on is power supply flexibility: My power supplies are all 13.8 volts, and my battery usually peaks at 13.3 volts. The rotary switch lets me find a voltage very close to the ideal 12 volts.

I used 1N4007 diodes because I have a roll of them, they are only 1 amp diodes, and do the job (with little margin, but I'm OK with that).

Yes, the dropped voltage is turned into heat (~3 watts), but I have a big LiFePo battery, and there's no chance of RF noise as can happen with a cheap buck-converter circuit.

73
Andy
WM8Q

On Wed, Dec 15, 2021 at 08:32 PM, Al Gritzmacher AE2T wrote:

just fed at the end with a 39:1 (not 9:1) transformer

I've not heard much about the 39:1 variety.? The 49:1 version works great, though.

I think it would be a good idea to limit ordering to one per customer with this small batch.? It would be nice if those who did receive one of the first batch QDX's would hold off ordering from this batch......

73 Dave AE9Q

I'd recommend a dipole. If you have 65-70 ft of that 18 gauge wire, you can use that.

Dacron cord will do fine for support line. Electric fence insulators will probably be able to be used as end insulators. Maybe even the center.

You will need a BNC connector to plug into the QCX+.

I'll recommend for a first antenna to just get some 50 ohm coaxial cable. Nothing big, don't worry about loss. Just enough to reach the radio. RG-58, RG-8X, even RG-174 would be fine. If you have 75 ohm coax, you could use that as well.

Strip, twist, and solder the coax to the antenna wires at the center point. Don't worry about baluns or fancy center insulators. Just support the coax somehow by fastening it to the insulator, and make it waterproof with some silicone caulk or tape or both.

Put it up as high as you can, but don't obsess over it if you can't get it 100 feet in the air. Even 20 ft will make contacts. If you can make an inverted vee, and get the center high but the ends slope down, do that.

An antenna analyzer is not essential, but makes the job easy. You'll probably want some kind of SWR measurement device. Many of them won't work at 5 watts, though. If you can borrow one, that works!

The most important thing is to calculate your wire lengths carefully and measure carefully, then leave a little extra - like a foot at each end. Fold it back and twist it loosely along the antenna. If you need to lengthen it, you can unwrap it.

If you measure carefully, even if you don't have a SWR meter, it will probably be close enough to work. You can always fine tune it later, but don't let perfection prevent progress.

There is not much easier an antenna then a 40 M dipole or inverted vee. If that's not doable, you might consider a end-fed half-wave. Same amount of wire, just fed at the end with a 39:1 (not 9:1) transformer which you would need to build or buy. Another option might be a vertical. You can hang 33 ft of wire from a tree and put a counterpoise/radial system at the bottom. Pretty much the same amount of wire to start with. That's physics... A vertical won't need any special transformer at the bottom.

But get on the air with whatever antenna you can muster. You'll be surprised how well you can do with a simple antenna.

I'm wondering, is there any limitations on these? One per customer, or people who didn't get one in the first round? They'll probably be gone in a flash!

addendum to original post.? When I power up this VFO/gen always shows reset...... then done!? Then it goes to the frequency screen!
syd

I just got back to working on this thing. Everything but the LPF band switching relay kit is installed. When I power it up without the relay kit installed, I get the initial QRPLabs start up screen and then it goes directly to the main frequency display.? Then the top display line shows 10,000,000 and the 2nd line shows 0? 010,000,000? 00 and the 2nd line on the screen is continually blinking! None of the buttons and rotary control do anything! Where do I start on this one?
73/wt1v

Or use the same method that is used for vanity callsigns - a lottery.
--
Julian, N4JO.

...or dig into your junkbox and put a <= 28k8 bps dial-up modem between the webshop server and "the Internet" to ease the burden on the server :) Much cheaper than replacing the server HW :)

73/SM6LKM

Ryan Flowers wrote:

I say sell them in batches of 10, spaced out evenly over the course of a week, so that the server has a fighting chance :D :D :D

--
Ryan Flowers - W7RLF

This is a great, rugged end fed that includes the radiating wire (even though you already have some) for about $40:??



He's out of stock now, but it goes in and out of stock regularly - just sign up to be notified.? He specifies less than 2:1 on 10, 15, 20, and 40 without a tuner.? I have just tried it on 20 and 40 and without any adjustments and had about 1.5:1.? Without a tuner and deployed in an inverted "L" configuration, this is a pretty minimalist, quick deployment antenna.??

I saw a review recently of a Chameleon antenna that was almost identical to this one (with a winder, exposed torroid, etc.,) and it was about 3x the price.? As rugged as the Chameleon?? Probably not, but with care, you can likely use it for years.

By the way, Jason, KM4ACK, has great videos on Raspberry Pi, Winlink, and other things of interest to hams on YT.??

73

There should be a betting game on how long it will take to sell out. I say ~6 minutes :)? Great work on the updates btw!

On Tue, Dec 14, 2021 at 05:17 PM, Shawn Reed wrote:

Are you speaking from experience? Yea, I forgot and left out the word "empty". It does make a difference, to your point. 73, sreed. kf7yff.

100% kidding, Shawn.? I have brass laying all over my office.? I've used shells as pry bars, screwdrivers, and likely as a hole punch too, but mostly as fidgety widgets while I am on work calls.??

Nice job on your protective case.? In fact, all of you guys are doing a good job.??