9cm Transverter
The above shows my 9cm transverter. It gives about 5W in 3400MHz. The boxes are rather old but still work fine after adjustment of all currents. The PA has 46dB gain which makes a attenuator necessary.
transverter component side
This photo shows the assembly side with the RF transistors. The other side carries the filter cups aß Well as some other larger components.
transverter top side
The small box ist the oscillator/multiplier and the other one the transverter.
G8ACE OCXO at 103.5MHz
103.5MHz oscillator briefly measured with R&S FSP30..
PN Plot G8ACE OCXO
I think above 1kHz the PN figure is determined by the FSP oscillator.
Does someone have a better measurement of such an oscillator, especially above 1kHz up to 200kHz ? Unfortunately i do not have a better PN testset.
The following picture shows the cold-start behavior of the OCXO from room temperature to 60 degree celcius. The X-axis shows time in seconds and the y-axis frequency in Hz.
G8ACE OCXO Startup
Sequencer for Transceiver and Transverter sequence control made around a Attiny2313. It can switch a RX/TX relais lowside, a PA supply highside, has “active” and a “TX inhibit” outputs. Furthermore there is a input to lock the PTT from a second sequencer (switch on the RX/TX relais only). There is an extra 7bit output driver that is in that example used to drive a pulse controlled RF relais.
This time no operation from hill. Just a few QSO from home. HiQSDR + ME2HT-PRO + PA + DK7ZB Oblong. Few hours of operation saturday evening and sunday afternoon. 78 QSO and about 18000 points claim.
The screenshot shows the great Tucnak log.
Some signals look very awful on the band…
I will not tell who it was ;) Hopefully the signal can be improved.
The weather in JO60OM was obviously quite good compared to other contest locations. A nice and warm Saturday, no rain during the night and sunny sky at Sunday morning. In afternoon it started raining and the rain continued until we were back home.
The equipment was running quite well. 13/9/6cm was operated by 2 operator new to microwave under the DN5TA training call. The 23cm operation was nice with ODX G3XDY about 860km. But i had the impression that the activity is declining each contest. You really need to push the people in chat in order to get QSO done. Between 0100UTC and 0400UTC even the chat activity almost stopped. The band was empty.
Here you can listen to the ODX QSO with G3XDY:
Some pictures:
23cm signals are very wideband sometimes
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.