Date
1 - 19 of 19
RFzero as a GPS referenced FST4W transmitter
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Rob Robinett
Steve KD2OM is transmitting FST4W-300 on 630M using an RFZero https://rfzero.net. Since they are still not available for sale I had forgotten about that device, but it includes a GPS receiver and a high quality oscillator, so it could be a good candidate for a low cost FST4W transmitter. It creates the 4W signal by modulating a So5351, so the modulation quality may suffer from the same problems as the QDX. But since it is out of stock for an indefinite time, for now testing it could only be done by looking at Steve's signals. |
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Nice to hear of the RFZero being used for FST4W.
However, looking at wspr.rocks other than Steve's own decodes I only see decodes to wsprnet from Jim WA2ZKD. As far as I can see Jim is not reporting to wsprdaemon extended spot tables from WD_3.0.3.4 and so I can't see what the spectral spread is (column 'metric' in wsprdaemon_spots_s on logs3.wsprdaemon.org). It is possible that excess spectral spread is one reason why Steve's spots have not been received by Tom WA2TP, who has, for example, recently decoded FST4W-300 spots from K8HTL at 1035 km
Gwyn G3ZIL |
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Erwin - PE3ES - F4VTQ
The RFzero has a low power output < 20mW. Would a RF-amplifier be needed ?
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Gwyn, I am pretty sure the antenna is the problem. The output of the RFZero goes to about 400 feet of 75 oHm CATV hardline then a 9:1 transformer to a 300 foot wire that is about 6 to 8 feet off the ground. AE2EA can also hear it but he is only transmitting FST4W-300 not receiving, his receiver is on WSPR. I am in process of getting a 5 watt amplifier and inductors
enough to tune an inverted L through much less coax, It should get
out better then.
73 Steve KD2OM
On 10/8/22 08:41, Gwyn Griffiths via
groups.io wrote:
Nice to hear of the RFZero being used for FST4W. |
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The output is +13 dBm. so yes it needs an amplifier. I have one
with output of +27 but it is not online. On 10/8/22 12:34, Erwin - PE3ES - F4VTQ
via groups.io wrote:
The RFzero has a low power output < 20mW. Would a RF-amplifier be needed ? |
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Gwyn Griffiths
Thanks for the additional detail, Steve
I find it hard to know at MF/LF whether the operator provides the tx power out or an estimate on the much lower ERP. 73 Gwyn G3ZIL |
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You are right Gwyn, I actually did not even set the value for tx out. When I get the loading coil and amplifier installed it should be an EIRP of 0.11 watts according to the calculator.
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Steve . On Oct 8, 2022, at 09:09, Gwyn Griffiths via groups.io <gxgriffiths@...> wrote:
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Jim Lill
The PA power versus ERP disparity exists on all bands but yes, it is worse on LF/MF -Jim WA2ZKD
On 10/8/22 09:09, Gwyn Griffiths via
groups.io wrote:
Thanks for the additional detail, Steve |
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I am now transmitting FST4W-300 at +10dBm into a Butternut HF-6V on 20 meters with the RFZero.
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The feed line is 150 feet of LMR-400. Steve KD2OM . On Oct 8, 2022, at 10:47, Jim Lill <jim@...> wrote:
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Gwyn Griffiths
Steve
The spectral width reports from Jim WA2ZKD around 1630 UTC yesterday show no more than 9 milliHz - which is excellent. The method of stepping the frequencies of the synth in the RFZero is not leading to any significant spread. 73 Gwyn G3ZIL |
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That is good to hear Gwyn.
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Steve . On Oct 9, 2022, at 03:05, Gwyn Griffiths via groups.io <gxgriffiths@...> wrote:
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Rob Robinett
Hi Steve, Here is a chart of the spectral spread of your FST4W transmissions over the last 12 hours as received by your Kiwis. Those spots are dropped by wsprnet, because the tx call is the same as the reporter, but they are recorded by wsprdaemon.org. The spread was impressively low overnight but since 10:30 UTC there have been some big values. Did the RFZero start to experience ambient temperature changes about then? Since there are gaps in the spot record, I also wonder if you are spotting every transmission. Rob  On Sun, Oct 9, 2022 at 5:46 AM KD2OM <steve@...> wrote:
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My thermostat has a setback so I imagine that the temperature of
the case might cool down about 0300Z and warm up about 1000Z. I
have some styrofoam I can make a insulated box that will help with
temperature stability. The RFZero is in a Hammond box so no air
movement there, some users put some foam on top of the RF section
but I don't think I need to do that. At the moment, 1415Z I see my cache is very full and wsprnet shows no uploads from anyone over the last hour so I guess it is hosed.
Steve On 10/9/22 14:07, Rob Robinett wrote:
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I put the RFZero in a cooler with an insulated top. It should be pretty temperature stable after the cooler temperature adjusts to the room.
Steve |
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I have changed the sequence to run 12 times an hour, the maximum.
Steve |
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Rob Robinett
That is excellent. In the last hour your WD client has spotted every one of your transmissions. Amazingly, EA8BFK is spotting you very frequently   On Mon, Oct 10, 2022 at 4:52 AM KD2OM <steve@...> wrote: I have changed the sequence to run 12 times an hour, the maximum. --
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This afternoon I changed the antenna on the beacon from the 3el yagi to the Butternut HF6-V.
Steve |
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Rob Robinett
I wondered why your SNR dropped earlier today. On Thu, Oct 13, 2022 at 2:31 PM KD2OM <steve@...> wrote: This afternoon I changed the antenna on the beacon from the 3el yagi to the Butternut HF6-V. --
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I switched it about 1940Z
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. On Oct 13, 2022, at 17:33, Rob Robinett <rob@...> wrote: |
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