Building a Pixie 2 QRP Kit (Ham Radio) Chapter 2

UPDATED NOTE, MAY 2008:
This is an old video from a year or more ago, when I was just getting my feet wet with building some HF radio kits. The Pixie is a great place to get started. I don't have a great deal of knowledge of radio theory, but this was educational in the visceral sense that I got to touch and feel the static and sounds of the HF spectrum. As far as being educational, well, it's not. Just enjoy this panorama of my small circuit board built on the kitchen table.

I finally got the Pixie to stop oscillating (motorboating) uselessly and to start sounding like the actual band. The problem is it has no selectivity, and broadcast interference comes in with the 7.04 traffic.
Also, the QRP calling frequency in Japan is different than the States, so there is a lot of RTTY traffic on the frequency.

Category:

Howto & Style

Tags:

• QRP
• Pixie
• homebrewing
• ham
• radio
• KC7FYS

[kc7fys]

sz42781 SAID:

im building a new transmitter with a 74hc240 ic chip, they reccomend a 50 ohm antenna. I have a uniden scanner antenna with a bnc connecter do you think this will suffice LOL? If not would a wire antenna work decient?

[kc7fys]

Yes, for receiving. If you want to transmit--and you will remember from the Ham Test that a 7.040 meter antenna is half that wavelength, all of that wavelength. You need some sort of SWR meter to know if you have a decent 50 ohm 'load' as they say. If it's not 50 ohms, you probably won't get much if anything in the way of signal out. Low power radio is all about the antenna. You want it to be perfectly resonant with an SWR of 1:1 for this transmitter.

[sz42781]

I see do you think say a radioshack would sell a 50 ohm antenna?

[kc7fys]

Do they sell wire? Yes. The 50-ohm part is you measuring it. For the Pixie, what is your frequency of interest?

[sz42781]

I may have you confused or may just be confused myself whatever the case, I am building a transmitter called "radio habana cuba ultra simple transmitter" you can google it to view the diagram, I orderd all the parts. On the diagram it shows a "50 ohm antenna", for all I know thats some sort of ham antenna. I just want to know how I can brew one or get one easy and cheap. Thats why I ask.

[kc7fys]

It is any antenna with a feed point impedance of 50 ohms. As long as we are googling, google that. The RHCUST lists crystals in three frequencies--which one are you using? If we know that frequency you know the length of the antenna to make it 50 ohms. A wire antenna for 7.040Mhz is 66.48 feet long. Two pieces of wire 33.24 (10.1 meters) with the radio in the center--a simple dipole. This is a 50-ohm antenna. There are other designs, but this is one. What is your callsign? I'm Jonathan KC7FYS

[knikk77]

Sounds like SSTV comming in there?

[romeoneverdies]

how about adding a transistor instead of the switch ?

[romeoneverdies]

50 ohm has nothing to do with resistance its the impedence of the antenna since most coax are 50ohm or 75ohm (for cable & satelite TV) so taking that to account its not realy the 50ohm part thats troubling its the wavelength thats important

as you want to get closest to either full length half or quarter length the closer you are to the full length the better the emission/reception for that frequency (hence wavelength )

[sz42781]

where could I get a schematic, and couldent you power it on and off to everytime you key to stop the carrier? IDK, looks cool though