ICOM AH-4 tuning aid with any radio

 Somehow, you end up into an ICOM HF eco-system.

You have an IC-7300 or 7100 or 7000 or anything else; a radio that can do HF and you also have an IC-AH-4 the "wonder ATU" from ICOM.

You mod it to be more modular and portable as I did, ready for field use.

Maybe you want to use some other radios on the same antenna system or you want to go portable with a Xiegu G90 and you said to yourself: "I could put that AH-4 to good work but the ATU will not work with anything but ICOM radios".

Well, you may be wrong!

The AH-4 can and should be used with other radios because it is a small gem! But how?

A small independent control box can be used with other radios to tune various antennas, from wires to loop antennas and this is what I done recently.

It is in a crude form, maybe I will make it with the help of a microcontroller or maybe I will leave like it is now because, it is working well!

What do you need?

-ICOM AT connector;

-One Red and one Green LEDs

-Two PCF817 or similar optocouplers;

-Two 1N4148 or 1N4001 diodes (not mandatory);

-Three resistors between 1.2 KOhm and 2.2 KOhm (these values where tested);

-a temporary SPST push button;

-a small test PCB or any other solution to mechanically fix all together.

The schematic:

How this is working?

Power up the box. The Green LED will lit.

START and KEY have 5V (UP).

Set the radio to 5W in carrier mode (AM, FM, CW) and press PTT or CW Key.

Momentary press the button TUNE. The RED LED will lit.

The START line (from radio to ATU) will go down; the ATU will respond with KEY going down for the tuning cycle (request for carrier). Side note: if you didn't press the PTT or the CW Key before pressing TUNE, now it's the moment to do that!

During the tuning cycle, the AH-4 will request from the radio (which is not connected to the control lines) to transmitt a 5 W carrier. 

Thus the IC-1 LED will lit and the corresponding transistor will keep START line down as long as the tuner need for the tuning cycle. Keep PTT or CW Key pressed on the transmitter.

When the RED LED is going off, the tuning solution is achieved.

Note: there are situations when the tuner will not find a solution for the antenna; the RED LED will go off and will lit again, the tuner will start a second sequence then will go in bypass mode.

I suggest using a small SWR meter between the radio and the ATU or watching the built in SWR meter to be sure a tuning solution was aquired.

This is my version:

The LDO is not used, it is for "further developments and upgrade"!

Yes, I know, it's ugly! I don't care about at this stage. 

It is temporary and it's working. 

The next version will be with a nice MCU, WiFi and Bluetooth controll and probably with RF sensing for auto-tuning!

Kidding but why not trying something like that? 

Are you a brave ham?

73 de Adrian YO3HJV

Some considerations about voltage readout on radios

 From time to time, in discussion groups some fellow hams start worring about the voltage drop on the radio readout.

This is from a Xiegu G90 group:

> However, the 0.9 voltage difference was still there. I am fairly sure now the

> difference is due either to inaccuracy of G90 volt meter. (I do know it reads

> 0.2 volts low in receiver mode) or there is something internal to the G90

> causing the drop

I think some theory must be exposed to help users to understand what it is about the voltage readings in these radios (and others as well).

The voltage is measured with an ADC (Analog to Digital Converter) which "translates" variable voltages into digital variables.

One important thing to understand is "resolution" which is the lenght of the number that store the analog voltage value.

In our case, the ADC input of STM32F4xx can operate in 6-bit, 8-bit, 10-bit, and 12-bit configurable resolution.

Another important value is the maximum voltage that can be applied to the ADC input, which, in our case is 3V3.

Based on the datasheet of the uC, we can safely assume that the voltage is measured in 8-bit resolution (best resolution without some tricks that involve supplemental processor cycles which are precious because they are time-consumer in a uC which also have to do DSP things), 

Resolution = ( Operating voltage of ADC ) / 2^(number of bits ADC).

Therefore, in our case:

Resolution = 3.3V/2^8 = 3.3/255 =12 mV.

This are the "steps" in which the voltage is measured in 8 bit resolution. 

BUT! There is a big caveat here...

We cannot measure with this resolution the input voltage as is much over the 3.3V after which the input of the ADC will be destroyed!

So we put in line a voltage divider!

The divider will have to accept at least 20V (because the radio accepts input as much as 17V in normal operation.

Let's find out, what is the voltage divider ratio in our radio...

If we look on the schematic,  Xiegu G90, the voltage divider is made with R63B and R67B 3.3KOhm and 470 Ohm respectively, which gave a ratio of 1:8 which means the resolution of the internal voltmeter is 0.096 (roughly 100mV) and the maximum voltage is 26.4 V!

So, any variation in the input voltage of more than 101 mV will be shown as a ... surprise, 200mV or 0.2V!

Simply said, the radio cannot show variations less than 0.2V!

As for the big variations when transmitting, again, from the schematic we can observe that the whole PARF components are tied to +13V.

The voltage tap used to measure the voltage is well beyond some components that will present a certain resistivity:

-power cord;

-fuse receptacle;

-RFI choke with both ground and positive leads;

-two MOSF-FETs used for reverse polarity protection and PowerON.

So, a 0.2-0.5 Ohm is a decent value for all of these and all of the above could explain the voltage swing measured by the internal DMM.

I think this will give a reason to enjoy the radio without worring about that voltage readout!

Cheers, 

Adrian

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Cateva module amplificatoare de radio frecventa integrate.
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Input power: 100mW

Output Power: 20W (max. 25W)

Datasheet.

2. MITSUBISHI M67729H2  - 170 Lei

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Minimum frequency: 450 MHz

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Supply Voltage: 12.5V (max.16V)

Input power: 100mW

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Input/Output impedance: 50 Ohm

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Maximum Frequency: 160 MHz

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The bands were full - Ham Spirit Contest

 

HAM SPIRIT CONTEST

“ No political, religious, military or commercial
purposes are pursued in the amateur radio service”.
The Amateur’s Code by Paul M. Segal, W9EEA (1928)

Based on the radio amateur code,
the «Central Siberia DX-club» decided to establish
the Ham Spirit Contest.

Contest Period:

Two Ham Spirit Contests will be held annually.

CW Ham Spirit Contest:
Start: October 29, 2022 at 06:00 UTC.
End: October 30, 2022 at 05:59 UTC.
Bands: 160m, 80m, 40m, 20m, 15m, 10m.

SSB Ham Spirit Contest:
Start: November 26, 2022 at 06:00 UTC.
End: November 27, 2022 at 05:59 UTC.
Bands: 160m, 80m, 40m, 20m, 15m, 10m.

Objective:

Radio amateurs from all over the world who have a radio amateur license are invited to participate.
The goal is to improve amateur operating skills by conducting 2-way radio communications with as many amateur radio stations around the world and from as many ITU Zones and square Fields of the QTH Locator as possible on the HF bands.

Entry Categories:

Single Operator Category:
a) SOAB - High Power: Total Output Power must not exceed operator’s license limits
b) SOAB - Low Power: Total Output Power must not exceed 100 Watts
c) SO Single Band: Low and High power - single nomination. Competitors may operate on all bands, but only on one of them can apply.
One person (the operator) performs all operating and logging functions.
The entrants may use QSO finding assistance technology or other source that provides call sign or multiplier identification such as CW decoder, DX cluster, DX spotting Web sites, e.g.
There is no limit on band changes.
Single operator stations are only allowed one transmitted signal at any given time.

Multi Operator, Single Transmitter, High Power
Only one transmitting signal is allowed at any given time.
Exception: One, and only one, other transmitted signal may be used if it is on a different band from the run transmitter and the station worked is a new multiplier.
There is no limit on band changes.

Alternate CQs on two or more frequencies using the same band is prohibited.
Output power (PEP) is limited by the terms of the owner's license.

All operators must comply with the rules governing the operation of amateur radio stations in their country.

Contest Exchange:

Exchange number consists of a signal report RS(T), number of their ITU zone and QTH locator square Field.
Examples: 599 27JN, 599 28JN, 599 42MM, 599 42MN, 599 32NO, 599 32OO. The ITU zone and
Squares Fields should not have separation to put them into log.

Scoring:

The QSO with station in your own ITU zone, regardless of the square, count one (1) point.
The QSO within your continent but with a different ITU zone count three (3) points.
The QSO with a different continent and ITU zone count five (5) points.
The QSOs with /MM stations count three (3) points regardless of where they are.

Multipliers:

The multipliers on each band are various combinations of ITU zones and Squares Fields. Examples: 27JN, 28JN, 42MN, 42MM, 32NO, 32OO are six different multipliers.

Final score:

The final score is a result of Total QSO Points multiplied by the total sum of worked multipliers.

Logs Submission:

Logs are accepted ONLY in electronic form in CABRILLO format.
Logs are loaded through the Web interface of the site https://www.ua9qcq.com.
All LOGS must be sent WITHIN SEVEN (7) CALENDAR DAYS after the end of the contest.
Any log received after this date is accepting for CHECKLOG only.

QSOs are not counted in the following cases:

- if the QSO is not confirmed by the correspondent's logs;
- if there are errors in the call signs or/and in the received control number;
- the QSO time differs by more than 3 minutes in correspondent's logs;
- if no report is received from the correspondent or/and the correspondent is “unique” (call sign
occurs in less than 3 contest logs);

Awards

Plaques are awarded to participants who performs the best three results in each of the categories.
Electronic certificates will be awarded to everyone who submits an entry.
The winners of the multiplier territories (Examples: 27JN, 42MN, 32OO … etc.) in each Entry Category will be awarded by еlectronic certificates
Amateur radio or other organization, as well as individual radio amateurs, may establish and sponsor their own awards.

Contest software:

N1MM, N1MM+, TR4W, DXLOG, 5MC, AA-test. And any other loggers adapted for the HAM SPIRIT contest.

Identifier QTH locator Sector: