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PA for 70 cm transverter

February 2, 2020, 5:48 am
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From BG7SGM, I ordered a PA module for 70 cm:
It is capable of delivering appr. 20 Watts RF at 70 cm. The module uses a M57704H.

I installed the module in the 28 - 432 MHz transverter:



A good heatsink is required. For the first time I used the repeater shift mode of the FT450. For 70 cm repeaters, in The Netherlands the repeater shift is 1.6 MHz. I also had to insert the CTCSS frequency of 88.5 Hz. I made a short QSO with PA0WBS via the Rotterdam repeater (430.300 MHz out). 


A quick measurement showed that the transverter delivered 15 Watts RF. Now, the challenge is to work in digimodes and see what is possible (FT-8 in particular).

See bg7sgm.taobao.com  and eBay for more RF products from BG7SGM (use google translate!).
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70 cm FT-8 contest

March 12, 2020, 12:48 am
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Yesterday evening I participated in a 70 cm FT-8 contest. A good opportunity to test my 28 MHz - 432 MHz transverter.
I was able to make a couple of QSO's (PA3BGQ, PC4L, 2E0NAQ..).


eQSL from PC4L


The QSO with 2E0NAQ over a distance of almost 200 km was very interesting:


70 cm FT-8 contacts March 11, 2020


PC4L, Marcel, sent me an e-mail showing that my signal showed some frequency drift of appr. 10..50 Hz. This is certainly an anomaly that needs to be fixed.
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4 m transverter

March 29, 2020, 6:18 am
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With the excellent designs of Serge, UT5JCW ( http://transverters-store.com/ ) I completed a 4m transverter:



The unit operates between 70 ... 72 MHz with IF (from my FT-450) between 28 ... 30 MHz. 

RF output power is appr. 10 Watts.


Although, I do not see much activity on the 4 m band, I spotted some stations operating in MSK144 on 70.175 MHz. Maybe that is something to focus on coming days.

Circuit diagram 28 <=> 70 MHz transverter

Transverter board
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Restoration PSU FP-4

April 22, 2020, 4:34 am
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With a rather simple circuit I was able to restore a Yaesu Power Supply Unit FP-4.

The PSU is almost 40 years old and the internal original circuitry was damaged. The transformer, diode bridge and 6800 uF capacitor were still ok.














I found this circuit to replace the existing electronics:


PSU circuitry


Soldered this small circuit on a vero board and installed it in the housing:

Restored PSU

Now the FP-4 PSU is up and running:


Note: PNP Power Transistor MJ2955 may be replaced by MJE2955, TIP2955 or 2N2955.



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50 MHz signals from India

April 27, 2020, 12:45 am
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When switching off my radio gear yesterday evening I was suprised to find a part of an FT-8 qso from India (QTH loc. JQ05) on my screen !

These were certainly the most distant 50 MHz ham radio signals I ever received:


QSO between VN4VUP and 8U8MBJ on the FT-8 screen.

What kind of propagation must this have been ? Multihop sporadic-E ?


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Good Es propagation on 4m

May 30, 2020, 12:48 am
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Yesterday,  good Es propagation on 70 MHz was present in the direction of Spain and Eastern Europe.




With 10 Watts from my 4 m transverter I made FT8 QSO's with HA5WA, EA6VQ, EC1A and EC1AJL.


Es propagation, May 29, 2020 @ 70 MHz



eQSL confirmation from HA5WA

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70 cm repeater Zierikzee

June 6, 2020, 1:14 am
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On the capital city of the island Schouwen-Duiveland a few km's south of me, the 70 cm repeater PI1ZLD in Zierikzee supports the Zeeland area.

The output frequency of the repeater is 438.400 MHz. Repeater shift is -7.6 MHz and CTCSS is 88.5 Hz. Antenna height is +55 m AGL.

The repeater used to be a DMR repeater, but has been converted to a regular 'analogue' repeater a couple of weeks ago.


St. Lievens Monstertoren
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VHF/UHF logper antenna

July 11, 2020, 12:13 am
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This week I finished a dualband logper antenna.

It is a design according to Gunter, DL9HCG.
Construction details can be downloaded here: https://dl9hcg.a36.de/

Logper antennas are also called LPDAs (Log Periodic Dipole Antenna).

The advantage of a logper (logaritmic periodic) antenna is its  large bandwidth combined with relative small dimensions.

I selected a 7-elements logper with following dimensions:




One starts with the construction of a dual boom

7 element logper



Measured SWRs:

430 MHz  1 : 1.4
145 MHz  1 : 1.6

First QSOs with the repeater in Goes 145.775 MHz and 438.400 MHz  PI1ZLD are promising.
http://www.pi3goe.nl


Logper pointing in the direction of the Zierikzee repeater
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No decrease in global CO2 concentration during the early COVID-19 era

July 15, 2020, 7:25 am
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At Mauna Loa, Hawaii, since 1960, the CO2 concentration is measured. 

Around 1960 the CO2 concentration was about 315 ppm (parts per million). In 2020 the concentration has increased to a level of about 415 ppm. Generally, it is believed that this CO2 increase is caused by anthropogenic emissions ('human caused' emissions) and is the main reason for global warming.





Fig 1 CO2 concentration at Mauna Loa, 1960-2020

Note: the 'sawtooth' pattern you see is caused by seasonal influences (the presence and absence of the green parts of trees/vegetation).

Since the start of the COVID-19 pandemic, the CO2 emissions from the burning of fossil fuels have dropped dramatically. It is estimated that the global CO2 emissions dropped with an average of 17% starting April 2020. Peaks of around 26% have also been noticed.
However, in the most recent graphs we do not see a decline in CO2 concentrations at all:



Fig. 2 Last 2 years

CO2 is a so called well mixed gas that spreads within a few weeks in the atmosphere. But even after a couple of months after the start of the corona wave, we do not see major changes in the Mauna Loa CO2 concentration trend.

Other global CO2 monitoring laboratories show the same behaviour as the Mauna Loa laboratory with respect to CO2 concentration.

One can consult the Mauna Loa data here:

https://www.esrl.noaa.gov/gmd/ccgg/trends/graph.html

This might be a good time to adjust the CO2-prediction models based upon the data gathered in the early corona period. The contribution of anthropogenic CO2 emissions to natural CO2 emissions might be far less then we thought. Administrations should be more reluctant with spending trillions on projects that might reduce CO2 emissions.
The most common greenhouse gas is water (water vapor/clouds). The effect of water as a greenhouse gas might be underestimated; Although the GWP ('global warming potential') of CO2 is much higher than that of H2O, the presence in the earth's atmosphere of CO2 (0,038%) is so much smaller than that of H2O (0.5%..7%) .

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nanoVNA

July 17, 2020, 2:07 am
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I just couldn't resist.

Ordered a nanoVNA that arrived yesterday.

I was able to do my first antenna analysis after looking at some youtube movies.



Here you can see a homebrewed 2 m antenna under test. A nice dip exactly on 144 MHz in the attenuation trace. The Smith chart shows almost a 50 ohms impedance (the green triangle near the centre).

It is an impressive toy for a few bucks (aliexpress, amazon). It enables you to analyse antennas, filters etc. from 50 kHz - 900 MHz !
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Fieldstrength meter

July 19, 2020, 7:38 am
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I replaced an insensitive VU meter by a 100 uA meter on my fieldstrength meter:



This meter uses a quadrupler circuit to increase sensitivity:



The GE-diodes (OA85) makes the meter useable till 500 MHz (estimate).
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144 MHz FT-8 activity

August 20, 2020, 1:45 am
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Yesterday, I noticed good FT-8 activity around 144.176 MHz.

I used my logper antenna and picked up signals from UK, ON, F and D.





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Audio-video website

August 24, 2020, 3:56 am
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I added a new website to 'nice web links'. It was recently launched by my son Johnno. He is an audio-video equipment product specialist.

Visit his website (Dutch only) here: http://audiobeeld.nl



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PI7CIS beacon

September 6, 2020, 1:52 am
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PI7CIS is a 2 meter / 70 cm beacon with QTH locator JO22dc (Scheveningen). The distance to my QTH is appr. 60 km.

                                                            PI7CIS

It transmits CW signals on 144.416 MHz (45 W) and 432.416 MHz (75 W). Antenna height is 42 meters ASL. More info: http://www.pa0c.nl/Pi7cis/pi7cis_vhf_beacon.htm

I was looking for a steady 70 cm signal for experimenting and improving the stability of my 28 - 432 MHz transverter and found PI7CIS. I am trying to improve the transverters 404 MHz oscillator stability. In the transverter there is a oscillator installed that is not temperature compensated (TCXO or OCXO). With a small resistor-heated heatsink on top of the oscillator I try to improve the short term stablity.


                                                        70 cm beacon on screen

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Casedemic, data against hysteria

September 17, 2020, 2:11 am
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 If you are interested in the science, statistics, graphs and numbers describing Covid-19, this video presentation of Ivor Cummins may be interesting for you:

https://youtu.be/8UvFhIFzaac

His message: Be aware of Casedemic Hysteria






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Magnetic Loop Antenna Controller

September 23, 2020, 6:17 am
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With Gerard, PA2G I am working on a magnetic loop antenna.

I have started with the Magnetic Loop Controller. The design of the controller is from Loftur, TF3LJ / VE2LJX.

https://sites.google.com/site/lofturj/to-automatically-tune-a-magnetic-loop-antenna

Frederik, ON5AI provides nice DIY-kits for this design

https://en.golb.be/


The hart of the circuit is a Teensy3.2 controller. I am using a steppermotor 17HS4401, which will drive the Vacuum-C of the antenna configuration.

There will be some interesting challenges: housing of the SWR-pcb, housing of the controller, interface with the HF radio, etc.


Status so far:


Magnetic Loop Antenna Controller


4 x 20 character display

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73 from St. Petersburg

October 17, 2020, 8:03 am
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Last wednesday, I made some HF FT-8 contacts. The QSO with Sergey, R1AV was one of them:








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Internet of Things

October 25, 2020, 4:23 am
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I read some interesting stories about the IoT lately. The ESP32 development board turns out to be good starting point to do some experiments with Wifi, Bluetooth etc.

I ordered a couple of this interesting, low priced, devices.

Time to get familiair with the Arduino IDE and the C programming language.




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ESP32 lessons

November 4, 2020, 1:13 am
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Past days I learned a lot about the ESP32 microcontroller. Internet teached me how to connect an LCD to the controller and how to read analog inputs.

I installed the Arduino IDE with the Espressif files to be able to program the ESP32 development kit in "C".

At this moment I have a working prototype of a CO2 sensor circuit. I used an MG-812 CO2 sensor.

This is how the setup looks now:

CO2 sensor setup


The circuit consists of an analogue and digital part:

CO2 sensor analogue circuit


CO2 sensor digital circuit




This is my first program in "C":

It was an interesting voyage to get the module in action. Lots of features are there to be discovered; wifi and bluetooth function, PWM outputs etc.

Note; The electrolytic capacitor of 10 uF between EN and GND on the ESP32 module was necessary to upload the program to the module. It took me a couple of days to find that out.


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ESP32 Simple Wifi server

November 13, 2020, 2:46 am
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I am exploring the Wifi possibilities of the ESP32 module. 

I found a sketch that enables you to switch on/off a LED via the module through an internet browser. I selected pin 2 as output, since this pin is connected to the internal blue LED of the module.

The LEDs on the ESP32 DEV module

The sketch includes the 'wifi.h' subroutine that sets up a steady wifi link to your local network.

I adapted the sketch and included two counters that shows you the number of switch on/off actions in your browser.

So now I have two-direction data traffic from the ESP32 mini wifi server to the internet browser. It works fine.

Part of the sketch:


 

This is how it looks like in the browser:




I am impressed by the Wifi capabilities of the small 3$ device.

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