Last weekend i had a negative surprise. Some noise from the desk and a lot of fume indicated that some electronic stuff burned.
Investigating the source of the fume i found that the mains filter of my old R&S SMY-02 burned away.
Fortunately i have connected it to a switchable mains distributor which prevented it from burning in my absense.
burned mains filter of SMY-02
I shortened the probe pins of my experimental pipecap filter to 5mm in order to get rid of the unwanted response around 7GHz. As expected the filter is rather narrow now and the attenuation increases a lot.
Marcel made some new measurements up to 14GHz in order to see how the suppression behaves. It looks a lot better now but you can also see that at the upper end of the measurement range the attenuation is very low (keep in mind that the probes are nice quarter wavelength antennas there).
The following picture shows the filter tuned to the 6cm band:
pipecap 5mm probes 5760MHz
The passband attenuation is now always somewhere in the range of 2..3dB.
Tuned to the upper end of the possible range you see that it behaves more than a lowpass than a bandpass ;) The passband gets a bit wider.
pipecap 5mm probes 10610MHz
pipecap 5mm probes 11815MHz
I would assume that it makes most sense to design the probes beeing quarter lambda for the frequency were the notch of the filter appears (or slightly above). Since this depends on the frequency you want to tune the filter to you need to consider that before you make the filter.
Pipecap filter dimensions
Triggered by some forum discussion about interference risk of operating repeaters in neighbor channels in 6.125kHz channels I was curious about the TX spectrum of my IC-E92. The measurement was done radiated. I checked for neighbor channel interference. You can see the delta values bottom right.
FM wide:
IC-E92 FM wide 1750Hz
FM narrow:
IC-E92 FM narrow 1750Hz
D-Star (only half span screenshot):
IC-E92 D-Star
You can see that D-Star is really the most narrow band mode. Using neighbor frequencies at close QTH still cannot be suggested but at least the interference will be less than for narrow band FM.
The picture shows a pipe cap filter experiment for 6cm. The 3/4″ pipe cap filter can be tuned between about 3.4GHz and 13GHz (see below).
Pipe cap filter for 3.4 to 6GHz range
The filter shown here approximately looks like that (screw is M4, 4mm diameter type):
pipecap filter example for 6cm
Some nice paper about constructions of pipe cap filters can be found at W1GHZ.
http://www.w1ghz.org/filter/Pipe-cap_Filters_Revisited.pdf
The measurements show about 0.4dB insertion loss. Do not expect to much suppression. As a simple RX image reject filter or for multipliers its certainly a good option.
S-Parameter for filter tuned to 5720MHz
However for my construction it seems that the rejection above the tuned frequency is not very good. According to the paper of Paul it seems i have choosen for too long probes.
S-Parameter for filter tuned to 4375MHz
[Update1 – wideband measurement]
DL2MRE provided some extended measurement of the filter up to 14GHz.
I have to say, that it looks better than i thought. I was expecting worse suppression at high frequencies due to radiation but it is ok. The resonance at about 13GHz might come from the 90degree SMA connectors. However the bandwith is rather large and has an unexpected shape. Might be some parasitic effect ? Thanks to Marcel !
pipe cap 6cm wide measurement 4-14GHz
[Update2 – unwanted response and tuning range]
Marcel made some more pictures with the filter tuned to different frequencies.
It can be seen that there is some unwanted respone of -15dB around 7GHz. This stays more or less static with respect to the frequency the filter is tuned to.
From above you see that the coupling probes have 11mm length. 11mm x 4 in wavelength equals about 6.8GHz in free space. So direct coupling between the probes is the most probable reason.
Filter tuned to 4380MHz
Filter tuned to 10368MHz
Another outcome was that the tuning range of the filter is very large from about 3.4GHz up to 12 or 13GHz.
Because of the static unwanted filter response i decided to open the cap again and shorten the probes to about 5mm (so about 15GHz). As described at W1GHz this has significant impact to bandwith and insertion loss of the filter. Now it is rather hard to tune it to the correct frequency. I will post some measurement results later.
Update
My 1st place for 23cm in the german competition survived the logcheck. I am happy with the result although i have to say that there was only one strong competitor DK2MN in the single-Op class. Compared to may the 1st place result is about 12k less. The same points would have been place 9 in the multi-op class this time. Thats quite some difference.
My unplanned 10GHz operation brought position 16 at least.
http://ukw-funksport.darc.de/ukw/result/2016/jun-2016a.txt
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I was operating from JO60OM, Hirtstein. The equipment was as few times before: HiQSDR, DB6NT Transverter, PA 2x100W, 1.5m dish and Quados8 antenna. The thing that worked well for the first time was the control of the antenna from VUSC log via my rotator control unit. Entering the locator, press ctrl-?, here we go.
It seems because of the thunderstorms in many regions over Europe the activity was not very high. Still i made 107 QSO and about 25000 points. ODX was YU1LA 840km via aircraft scatter.
Saturday morning before the contest i decided to take the 10GHz transverter and the 40cm dish with me. That was a good choice actually. Although i just operated that on Sunday and only in north direction i made 19 contacts. ODX was PA0BAT about 500km.
june 2016 rig after the contest
QRV with the DM7A team from Fichtelberg, JO60LK. We worked our various personal calls on 2m, 70cm, 23cm, 10GHz and 24GHz. The weather was sunny but very stormy.
On 2m we tried a tiny 2x2x5ele setup for 2 directions. The gain was somewhat low but still the ODX was about 850km with YU7ACO. We had two newcomer with us who worked on 2m.
Here an impression of the wind in JO60LK.
and a few pictures:
This time i had to stay home. I used the little time to check the equipment for 2m.
In the end i had 37 QSO in about 3 hours of operation time. Not a lot. Given that i just use a omni antenna i am still fine.
March 16 – stations reached
For some tests i finally succeeded to compile WSJT-X 1.7.0-devel with JTSDK.
https://sourceforge.net/projects/jtsdk/files/linux/
The documentation seems to differ from what needs to be done slightly. The difference was that i needed to place the jtsdk-xxx directory in my home directory and rename it to jtsdk. I used jtsdk to generate a .deb package. Find it below. Maybe its useful for someone.
I run a small Odroid U3 board with the Ubuntu 14.04.2 image from hardkernel. The board itself is obsolete meanwhile. Maybe the package can run on other ARM boards too.
wsjtx_1.7.0-devel_armhf.deb
I am not sure what dependencies you need. Please refer to the JTSDK readme if you need some guidance.
This is a screenshot of the software. I did not do a qso yet. So i cannot guarantee that it is really working well.
wsjtx-1.7.0-devel on Odroid U3
A evening of TX. The picture was made by DK1RS in a distance of 80km and shows my signal (horizontal line) during about half an hour. The crossing lines are reflections from aircraft +- Dopplershift. So far signal raises about 10dB compared to the direct path between Rainer and myself. WSPR cannot decode if the Aircraft Reflection is present because it cannot deal with the Doppler drift.
A simple project in between. This is a small quadrifilar helix antenna for the L-band. The measurememt does not exactly fit the calculation but for the first trial it seems ok. Probably the thickness of the material was not considered for calculation of the length of the loops.