Perfect Portable Antenna
The PPA-20 is an “end-fed Zepp” antenna shipped preadjusted for operation on 14.1 MHz. It should exhibit a VSWR better than 2:1 across the entire 20 meter Amateur band.
An end-fed Zepp is similar to a dipole in that its length is one-half wavelength at its intended operating frequency, so it does not require a ground system or radials like a ¼-wave monopole requires. The PPA-20 does require a counterpoise wire, approximately 3 feet in length, which can hang free and does not need to be connected to ground.
The radiating element is a flexible AWG-24 wire, approximately 33 feet in length. Do not alter the length of the radiating element or the counterpoise, or the antenna may not perform as desired.
The PPA-20 is rated at 2 Watts. Use at higher power levels is at the user’s risk, and Lazy Dog Engineering will not be responsible for any damage resulting from such use.
If you plan to use your PPA-20 in a permanent or long-term installation, you may wish to replace the radiator with one made of heavier-gauge wire.
Here are some links to previous articles describing the development of the PPA-20: The Perfect Portable HF Antenna, Part I, The Perfect Portable HF Antenna, Part II, The Perfect Portable HF Antenna, Part III, More on the Perfect Portable HF Antenna, Perfect Portable Antenna Now Available
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#1 by Craig at August 2nd, 2010
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Is there a Linux SDR software that your LD-1 can use?
#2 by admin at August 10th, 2010
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There is Linux SDR software, but my control software uses a USB driver supplied by the microcontroller manufacturer, Silicon Laboratories. Unfortunately, they don’t supply a Linux driver. I am really sorry.
The only way you could use it with Linux would be to set the LO frequency from a Windows PC, and store it in the radio’s flash memory. Then use the Linux machine to run the SDR software. There is something called “Linrad”, similar to “Winrad”, but I don’t know anything abouth it.
#3 by Bob at January 3rd, 2011
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I was wondering why your specs list the tx mic input as a “stereo” or two channel interface.
SO you must have a two channel soundcard mic input.
Using the words ‘cheap’ and “dongle” in the same sententence, cause me much frustration.
I do not understand why your units are built differently from the dongle units, or the cheap units, in that they have a monural input for the tx mic or key.
Please explain. I do not understand.Why make them this way when 99% of SDRs out there have one input.
Thanks ,
Bob, KG4RRN
#4 by admin at January 3rd, 2011
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The TX mic input isn’t really a mic input, and I don’t think I described it that way (I’ll have to check and correct it if I did). It’s an I / Q IF input from the souncard that’s used to interface the PC to the SDR, just as the SDR output is a two channel (I/Q) IF output which goes into the stereo line-in jack. When the transmitter module becomes available, I expect that most users will use two soundcards, one for the actual audio in/out with either stereo or mono connection to speakers and a mono connection from a mic. I actually use a USB headset with mic for this purpose. The other soundcard would be a high-quality (24 bit) high sample rate unit with “stereo” input and output between the SDR and the PC.
I’m assuming that you understand why a stereo connection is required between the SDR output and the PC when receiving. If you don’t, I’d be happy to explain it to you. The stereo connection for transmitting is really the same thing, just going in the other direction.
As far as I know, all SDR’s that use the soundcard for analog to digital and digital to analog conversion are this way. If you know of one that isn’t, I’d like to hear about it.