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Messages - SlowBro

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Ok that makes sense. It should work about the same as equivalent center-fed designs. I like the flexibility of the end fed and especially not having to carry coax.

New To Radio / Re: Do I need an SWR meter for a backpack rig?
« on: August 26, 2017, 03:05:50 PM »
Note to self: keep eye out for portable soldering iron.

Got five bucks?

Got a piece of wire, tape, and a Bic lighter?

Good point on the northern hemisphere. Just a quake in Calif long over due will send the entire northern hemisphere into the dark ages. Fuk-U-Shima was nothing learned from except cover ups. Foreign (US) companies supplied all that stuff and they built it on fault lines. What about Calif. In theory, the Southern Hemisphere has no nukes but in reality they may be stationed in Australia or at least on submarines. If that happens the whole world is in a mess. But I think the north would be worst, already is pollution wise. If one has to move far, weight and durability is an issue, and back ups -- more than one TX, more than one RX, spare components. Realistic sources of power. Solar panel, if there is sun getting through after such an event. Me thinks if something like that happens, whoever has batteries or knows how to make them is going to be the new billionaire, locally. Everyone will want batteries. Not sure what for, as aside from radio, not sure what is needed on batteries, lights I guess. People can learn to brush their teeth with sticks surely.

If I have to beat feet out of the northern hemisphere it would be after listening to the radio reports and committing to the direction of travel no matter what. Thus carrying a radio after taking off wouldn't be as critical; if I had to ditch the radio for some reason, I would.

I happen to have a number of 3V 0.42W solar panels from another project that I'm going to integrate into my pack radio. I'm going to solder them up and tape them together with cardboard and duct tape. Ugly but free 8)

Slowbro this may also be interesting for the Pixie if connecting EFHW wire 20m long is not a good idea, then you can use this:

Yep that's the aforementioned MEF-1. I found the circuit diagram and bought the one-twosies parts I didn't have so that I can rebuild said circuit on my PCB.

I just got my Pixie in the mail and if I get my act together I'll post pictures and a status update.

SlowBro, I could be wrong, but I wonder if just connecting an end fed with 20m long (half wave) to that Pixie directly is going to do any damage, and whether the 300mW to 1W (check it's output with a proper QRP power meter, it may be less than expected) will go into such an antenna.

I'm not going in directly, the impedance of an end fed is very high. Although it's been done before. No the antenna goes to the PCB and from there into a tuner then into the Pixie.

I'm wondering why build a multi band difficult to make antenna like a G7FEK if you can just use a simple dipole cut for 40m and fed with the very thin tiny coax?

It's the weight and expense of even thin coax. I like the end-fed, going to go with that first and see how it performs.

I think you meant down to 6MHz, that would make sense. I don't think it can be made to work easily or efficiently on as high as 50MHz?

I said 6M but I should have said 6m as in, six meters. I learned since creating this post that meters should be lowercase 'm'.

Ok thanks and what is the recommended minimum height in wavelengths the antenna end should to be off the ground if doing an inverted L, sloper, or inverted vee?

Right on cockpitbob. That looks like a good article. I'll review it before I settle on the final tuner design.

I had discovered the same since opening this thread. I had not given an end fed much thought until Gil recommended it and now I believe that's what I will carry in my pack. As you said, I don't need any coax at all and in fact I will just connect the antenna directly to the PCB.

The Pixie's BNC connector won't be installed and instead, two wires to another PCB which holds the tuner (likely the MEF-1) and SWR indicator circuit. A hole in one side to lock in the antenna wire strung up and out and another hole for the counterpoise. Will keep short lengths of wires permanently connected to the board and bullet connectors to add on the rest of the radial and 0.05 wavelength counterpoise. Plus the aforementioned fishing line to hold it up and take the strain. (Mason's line, you say. Interesting.)

I like the way they run the wire on the MEF-1. Takes all the strain off with no added components. By the way I found this page which describes a variety of ways to string an EFHW.

Other ways to get the line over the branch: A plastic water bottle, line tied around the neck. I like this once since there's nothing extra to carry; my pack has water bottles. Another way: A nylon sock with rocks in it. Tie the line around the neck of the sock. I may be carrying a nylon sock anyway, but the thought of it snagging and losing maybe my only other sock, I don't like that.

Also, I initially said "no tuner or SWR meter" because I saw them as heavy, expensive black boxes. Didn't know they can be made very cheaply with very few components 8)

New To Radio / Re: Do I need an SWR meter for a backpack rig?
« on: August 24, 2017, 11:28:35 AM »
Well I accepted from the beginning that marginal transmit and wide selectivity would be sufficient since I didn't want to go over budget. Gotta start somewhere. And yep, I saw that video, took notes.

Main concern is getting situational awareness during grid down or EMP. Info on nuke plants especially. If more than a few of those are going up in smoke we should beat feet out of the northern hemisphere. I'm betting that CW will last the longest and go furthest during grid down, and I shouldn't need to transmit very much if anything, I'm sure there will be enough people talking that I can just listen. So I string up an end fed, tune the varicap to find someone talking, plug in and tweak the center frequency on the CW filter. With the end fed I can use a variety of configurations and go DX to NVIS.

New To Radio / Re: Do I need an SWR meter for a backpack rig?
« on: August 24, 2017, 08:29:15 AM »
Ok but what about in the situation I describe? At home, I tune it. In the field, I put the antenna at about the same height. Would it be sufficient to say the tuner should be placed in roughly the same spot for both locations, or can they really vary that much?
Depending on the antenna resonance, e.g. if it is a half wave dipole, and thus quite broad band, then YES in general. And it won't do damage to the Pixie even if you transmit without an antenna (I THINK!). I've used a Pixie for 3000km QSOs but the problem was not just that my signal was very weak, I think it only put out some 350mW or so, on 7023kHz, but also that the receiver seemed very deaf! I suppose with so few components you cannot expect a sensitive receiver! Wide as a barn door doesn't bother me, I have filters in my brain-ears, but lack of sensitivity does. Other stations that were S9 were just copyable. If they had ALSO been using Pixies, no way would the 2-way long distance CW communication have worked. A pixie is a pretty poor choice. But that's just $5 including postage!

Here are good, I hear, QRP 1 Watters and there is a 5 W amplifier there too: they are single band TX/RX but tune a few kHz, I'm thinking to try one: -- at $47 each doesn't it seem a good investment to buy one for each band? If one goes missing, gets squashed, hit by a fly or gets stolen instead of your jewelry, then you are at least not QRT!

Maybe I will upgrade soon but I like the path I'm going because the Pixie circuit is simple enough to (mostly) understand and tweak and build on as time goes on. Well aware of the poor selectivity which I aim to somewhat mitigate with this low-pass add-on and also an LM567-based CW filter. The latter can "lock on" to one tone and filter the rest. I had most of the components I needed already for that, and the chip itself was 3 for a dollar USD, couldn't resist :-)

New To Radio / Re: Do I need an SWR meter for a backpack rig?
« on: August 24, 2017, 08:22:14 AM »
Just a comment on the LED SWR indicator (a.k.a. Tayloe or N7VE indicator).  One of the best parts of it is while you are in Tune mode you cannot hurt your rig.  The worst SWR your rig will see is 2:1.  If the antenna is shorted the Tayloe indicator presents your rig with a 25 Ohm load, and if the antenna is disconnected your rig sees a 100 Ohm load.   I'm a design engineer and to me some of the most brilliant designs are also the simplest.  The Tayloe SWR indicator is truly brilliant.

Yes indeed the design is brilliant. Based on your comments I searched around and found an SWR indicator that has specifically been tested on the low-power Pixie I'm building. Going to try that one instead of the one linked earlier. It requires two geranium diodes which I picked up on eBay, USD $3 for 5, US ship.

Does the variable capacitor need to be 250pF or could a 50pF varicap be used with 200pF additional fixed caps in parallel? I realize this reduces the tuning range but I only care about the lower portion of 40m.

Another question, what is the minimum height in wavelengths the antenna end needs to be off the ground if doing an inverted L, sloper, or inverted vee, like these? I've not found any recommendations anywhere.

Looks like a good article!

I had not given an end fed much thought until you recommended it Gil and now I am convinced that's what I want to carry in my pack. Reason being, I don't need any heavy coax at all. I'm building a small rig in a plastic box and will just put the antenna mount directly on the PCB.

I see the recommendation is for a 22 gauge radial. I'm going to try to get away with a thinner radial by using fishing line and taping the wire to that, relying upon the fishing line to bear the weight. (The combined weight may be heavier than 22 gauge, I don't know. But it is cheaper since I have all that I need on hand.) And will segment the radial for different bandwidths, connecting and disconnecting as needed. I bought some bullet connectors but I later found that inline banana power plugs used for RC car batteries may be a better approach.

Good stuff.

New To Radio / Re: Do I need an SWR meter for a backpack rig?
« on: August 17, 2017, 12:16:46 PM »
Thanks all! I'll try to remember to report my success or failure later.

On your advice I picked up the parts to make a tuner with SWR LED indicator. Simple and cheap circuit. For the antenna wire I will solder in spade connectors to alter the config between Windom, end fed, and dipole. Thus I won't have to pick only one configuration. I'll carefully match coax in the New Carolina Windom style having its necessary 10' of coax vertical, and a choke of ferrite snap ons and coiled coax at the end. That choke should only benefit the end fed and dipole configurations so it should make a great three-in-one portable antenna.

The radiator wire and center balun will be loosely taped to a very long fishing line. That line will do all of the load carrying and the wire can thus be thin (lightweight) and use spade connectors that would otherwise disconnect when strung between trees. No stress or load carrying on the radiating components. A rock on both ends, slingshot the ends into trees, pull both sides down, and tie it off.

Testing in a month or so and I'll try to remember to update this thread with my results.

By the way forum notifications don't seem to work. I don't get emails when someone replies.

New To Radio / Re: Do I need an SWR meter for a backpack rig?
« on: August 13, 2017, 06:53:27 PM »
Ok but what about in the situation I describe? At home, I tune it. In the field, I put the antenna at about the same height. Would it be sufficient to say the tuner should be placed in roughly the same spot for both locations, or can they really vary that much?

New To Radio / Re: Do I need an SWR meter for a backpack rig?
« on: August 13, 2017, 09:29:28 AM »
Yes that looks like the circuit I mentioned in the third post. The LED is actually the SWR "meter" and its brightness changes strength as the reflected power changes. Quite a simple and clever circuit, and should be simple to build and cost little and weigh next to nothing and take up little room in my pack. A win-win.

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