Hairpin modified antenna – estimated performance based on WSPR data analyse

So, we have an short antenna, easy to build and install. It was working in WSPR mode more than 3 days. It’s time to find the performances… and to see if our expectations are to big, or what can we improve.


First analyse is a simple one. Just go to VK7JJ site (http://wsprd.vk7jj.com/) and follow the instructions. You can see when you see a lot of useful informations about your antenna, the antenna location and propagation.

It looks fine… it’s only an example of useful info. But is not enough. The chart say you can work from YO stations from VK, JA, North and South America. Yes, using WSPR mode.

What about other modes ?


Let’s go to KP4MD site (https://www.qsl.net/kp4md/wsprmodes.htm#application) and download the mode-comparison excel file.

Using your WSPR data you can find if you can work a specific station in another mode (CW, RTTY, SSB, etc.).

Let start with the bad news…

After you shall download and process the data, you shall find that the probability to work VK7JJ in RTTY or SSB mode is very low to very, very low. Red colour is not good….

Let’s check other DX stations

Sorry, no K1ABK, no JA5NVN.


OK, dont panique, let see what can we work.

TF4X                        3927 km


MM7BWK              2544 km


OH3FR                     1867 km


So, if you want more, try to find if you can use a higher position or re-locate the position, or improve soil parameters, etc.

For example, my location is very unfriendly regarding the obstructions around me. As you can see in the graphs (from 1st part, VK7JJ site), the existing freeway to 310 degrees azimuth is confirmed by number of spots and the obstruction from 230 degrees (a new big house, etc.) is also confirmed by no data/spots on that direction.

40 m band – Hairpin antenna – Theme with variations (part 2 of previous article)

200mW WSPR test

After 2 weeks of testing the Hairpin antenna for 40 m band (the light model with Cu wires), it’s time to build the regular prototype with Al tubes. But, first off all, let’s play with MMANA- GAL to see what are the limits.

The main differences between classic Hairpin antenna and this model are:

  • The antenna is mounted on a metalic grounded mast.
  • The spacing between arms is larger to obtain a wider antenna

 

Now, let’s play with parameters.

  1. Spacing

Aluminium tube diameter = 24 mm
Hairpin length = 3 meters
Height from the ground = 4 meters
Ground setup = 14 / 5
Q capacitors = 500
R =50 ohms (+/- 1)
jX = -1 /+1 ohms

Higher spacer, better gain and Bw

2. Aluminium tube diameter

Spacing = 24 cm
Height from the ground = 4 meters
Hairpin length = 3 meters
Ground setup = 14 / 5
Q capacitors = 500
R =50 ohms (+/- 1)
jX = -1 /+1 ohms

Higher tubes diameter, better gain and Bw

3. Q capacitor

Spacing = 24 cm
Height from the ground = 4 meters
Hairpin length = 3 meters
Ground setup = 14 / 5
Aluminium tube diameter = 24 mm
R =50 ohms (+/- 1)
jX = -1 /+1 ohms

Vacuum capacitor (High Q), high gain but narrow Bw

Regular air capacitors, lower gain but wider Bw

4. Height from the ground (grounded mast length)

Spacing = 24 cm
Q cap = 200
Hairpin length = 3 meters
Ground setup = 14 / 5
Aluminium tube diameter = 24 mm
R =50 ohms (+/- 1)
jX = -1 /+1 ohms

More height, more gain and Bw

5. Hairpin length

Spacing = 24 cm
Q cap = 200
Ground setup = 14 / 5
Aluminium tube diameter = 24 mm
R =50 ohms (+/- 1)
jX = -1 /+1 ohms
Height = 4 meters

Too short, less gain. Too long, you can not tune the antenna (value of Cv1 will drop to parasitic capacity, or to zero)