WSPR with an attenuator
WSPR, like other QRSs modes gives an opportunity to be heard over a long distance, with very low power. The reduction in speed, can be translated directly into a reduction in power. Low speed and very low power is an excellent combination.
If I can work stations in many European countries with 500 mW to 50 mW in CW contest QSO’s, then it must also be possible with WSPR with 50 mW or with 5 mW.
This schematic shows an attenuator for a continuous input power of a few watts.
When set at 20 dB, this attenuator can be used with the FT-817 to reduce the power from 1 watt to 10 milliwatts.
With a “Power Attenuator” of 20 dB, you can reduce your power from 5 watts to 50 mW.
By adding this power attenuator, you can use your 5 watts QRP set, to transmit with only 50 mW.
Tip 1: Reduce your power by 20 dB, by using the sections of 3 dB, 7 dB and 10 dB.
The more attenuator sections are used, the more power can be dissipated.
Tip 2: When you use an attenuator for WSPR, please use 10 dB or 20 dB.
With a step of 3 dB, you will not notice any difference at all with WSPR.
Tip 3: WSPR over a long, long time on the same band.
Take the time, to see the absorbing layer, below the reflective layer, disappear.
Even if the M in MEPT would mean, to put your set under your pillow. Hi.
If you stay long enough on one band, you have the change to notice unexpected propagation.
The attenuator reduces the power during the transmission, but, since there is no T/R switch, the received signal will also be attenuated. With the attenuator set to 20 dB, the reception sensitivity will be 20 dB less.
The WSPR spot database
I regularly visit the WSPR Spot Database, to check out the “amazing” results of stations that use very low power. If the data is sorted by Miles per Watt, then the stations are shown, that cover great distances with just 1 milliwatt. (hi) Be creative in discovering your own interesting queries.
Do you want more than 50 spots. You can fill in 5000 or more (even 18000) in the field “Number of spots”. Go to the WSPR database >>
Please be critical towards spot with less than 1 milliwatt. These spots often contain stations with invented calls and unlikely locators. Most of the time there is something wrong with each individual spot. I remove all spots with less than 1 mW before an analysis.
I have until now, (2015) not yet transmitted with WSPR.
The focus of my activity, is the use of low and very low power in CW contest QSO’s.