Ok, I don’t know what happened… For some reason, no sparrow progress since Oct last year. Anyway, I am back, and working on the Sparrow again!
I have now done som basic tests of the T1. I decided to tune the MP-1 to somewhere in the 40 meter band and then try to match it with the T1 on the other bands. The initial setting of the MP1 was as follows:
This article gathers my previously posted blog entries concerning the FT-817 CAT. The blog entries have now been archived and are not available anymore; however, all info should be present in this article.
I have just completed the assembly of the T1. The power on tests from the assembly manual are all all right. I must wait with the functional tests till I am back in LMX, because I have no 50 ohm calbes here.
I have now finished the control board as well. All resistance checks passed. I can not do the LED test, because I do not have the diode tester here, it’s in LMX. In any case, I have been very careful when mounting the LEDs, so they should be all right.
I have now finished the last two coils, L6 and L7, as well. Looking back I think it was a very good idea to make the coils in the same order as described in the assembly manual: L1 … L7. It starts with just a few turns and increases gradually up to 29 turns on L7.
So, I have spent most of the time since saturday noon on building the T1. I have made good progress so far; I finished almost everything on the main board except the last two coils, L6 and L7.
By studying the graphs in the User Manual I have come to the following parameters, which are supposed to be good enough for CW work. Note that 80 and 40 meters can not be tuned independently, which is why the centre frequency on 80 meters is set to 3.6 MHz.
The FT-817 receiver is great in digital modes too. I find it, however, that normal operation the way I am used to do it, is rather difficult with the important functions hidden behind different menus.
The resonnance frequency of the ATX-1080 is adjusted by selecting the correct taps to connect (band change) and adjusting the telescope length for fine tuning on the given frequency. The radial length should have different lengths for each band as well. The original document describes which taps need to be connected and how long the telescope should be on each band, but says only that the radial length should be less than 1/4 lambda. Wimo, on the other hand, provides to pages of documentation in German, where they also give some start lengths for the radials. Also, a useful formula l [m] = 54 / f [MHz] is provided.