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Topics - SlowBro

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New To Radio / Do I need an SWR meter for a backpack rig?
« on: August 12, 2017, 01:27:38 PM »
Just bought a 40M QRP Pixie 2 kit off Fleabay. (Yeah yeah I know, not the best, but it'll do for now.) It transmits at under a watt. I'm aiming to keep it and either a Windom or maybe an end fed half wave in my BoB or bike trailer.

Since I may be placing these antennas in different configurations and heights depending where I can find a place to set up, I can imagine the tuner would need to be tweaked often for the best signal. Is an SWR meter strictly required in this situation or can tuning be guesstimated based on prior experience? I would think it'd be required if I used higher power, but I can't see that low wattage doing any damage to the rig if the antenna is not in an optimal location. I would just guess the tuner based on what worked in the past, for that particular antenna height.

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Hello! I've looked at ham radios since I was a kid but this week bought my first rig, a Pixie 2 QRP kit off Fleabay. (I know, I know. Not the best, but money is tight.) I'd like to grab and pack it in my BoB or bike trailer if there is a crisis, and I'll be keeping it in an EMP-resistant box until needed. Would be battery and/or solar-powered.

I've looked at various antenna designs and can't make a decision. Can you recommend an antenna type that meets the requirements below?

I'm "leaning" (pun intended) toward going with a tree-supported sloping Windom. Just slingshot a rock with line up a tree and pull up my wire. This should let me put the short end near the ground for less coax needed, and I already have a TV balun. (75 ohm - 300 ohm, that's 4:1 right? New at this.) They're supposed to be good for DX and when I want to change direction I just walk around the tree :-)

  • Backpackable e.g. less than a few pounds/kg and rolls up into a smallish package
  • Quick setup/tear down
  • No poles, will use trees
  • Less than USD $20 please. I already have some telephone wire, some TV coax, some Ethernet wire, a TV balun, some thin stainless fishing line. Oh and I bought a BNC balun for 75 cents that is typically used for CCTV to transmit over CAT5. (I don't know its ratio but I guessed 1:1?) I figure worst case I can hang the transmitter right on the dipole, but on the other hand that'd require me to place the dipole close to the ground to reach the transmitter.
  • Feed line any type but partial to TV coax for cost savings. The transmitter output is 50 ohms with a BNC connector so I bought a BNC-to-F adapter to let me use 75 ohm TV coax. (75 cents.) From what I've been reading, the feed line loss going from 50 to 75 at 7MHz is acceptable and keeps within 1.5:1 SWR.
  • No tuner required, I'm sure I can ask around to find a SWR meter at the local clubs to tune it up once built.
  • Single band is acceptable. If absolutely necessary I can switch the crystal down to a shorter wavelength, also requires replacing the inductor on the Pi filter. I've read these Pixies can go down to 6M. But I want acceptable performance year-round so I'm trying to steer clear of higher frequencies and sunspot concerns.
  • Would like to be able to receive and perhaps transmit a few hundred miles/km but will accept loss of distance as trade-off for price and weight/size
  • Likely be doing more DX than local, getting an international perspective during a crisis could be useful. But I do also want to know of regional conditions such as nuke plants after an EMP, so maybe I do want to stick to local? I'd like your opinion on this as well. If local, could an NVIS be a better option?
  • I think I would be doing LOTS of listening and not much talking so biasing the design toward receive would be better.

Am I asking for a unicorn or is there a design with decent compromises for my situation?

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