VKV PA – July 2021

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20. August, 2026

Mapa spojení vo VKV prevádzkovom aktíve - júl 2021

The summer months are ideal for outdoor radio operations. That’s one reason why I headed back to the Vlčí vrch area near the village of Horná Súča. Compared to last month, there were several new developments.

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An amplifier with an LDMOS MRF9180 and an R2CW transceiver

The first is an amplifier with an MRF9180 LDMOS. I chose this type because I have a 28V power supply. I managed to build the amplifier and set it up to work with the R2CW transceiver. For contests, it’s a better transceiver than the Kenwood TR-751E. However, there’s also a difference in how the amplifier is controlled: when transmitting, the R2CW sends a positive voltage to the output, whereas most transceivers send 0V or a short circuit.

To make things more comfortable, I built a hanging table for the car. After all, it’s more comfortable to sit on a seat than in the trunk.

Hanging table with the R2CW transceiver and MRF9180 power amplifier

The weather was on our side; the forecast promised only a light breeze. Setting up the antenna and preparing the workstation took about half an hour. The last thing I wanted to do was start the generator. After all, the sound of a running engine isn’t exactly pleasant. But the generator wouldn’t start. Not on the first, second, third, or fourth try. Since it’s impossible to troubleshoot problems like this on a hill, I quickly disconnected the entire setup and switched to a Kenwood TR-751E powered by batteries.

Directional Map of VHF Operational Activity Connections – July 2021

I’m starting the VHF operational activity there with a slight delay, which is insignificant, but I’m quite disappointed by the forced change in setup. After all, 100W versus 25W represents an additional 6 dB, plus the benefits of the signal compressor and the quality of the R2CW transceiver will certainly make a difference.

Hanging Table for the Car

A big plus, however, was the hanging table. Adjusting the antenna was still done manually, but operating either the transceiver or the laptop was much more comfortable. The hanging table is attached to the headrests of the seats with two carabiners. It measures 120 x 30 cm. It’s more stable than I expected. Under heavier loads, it’s a good idea to shorten the tension cables to prevent the table from sinking into the seat.

What power settings are used in the VHF PA?

I used ON4KST more intensively because few stations responded to the call, and it’s also more difficult to make contact when searching. The average power output seems to be somewhere else.

For example, according to reports from this round of the VHF Operational Activity in OK, 58 stations reported their power output. The average comes out to 238 W, which is nearly 10 dB more than on my end.

Comparative Map of OPK Stations from VHF PA 07/2021

You can view the map of contacts in OK, composed of two images. Where the lines end with a small circle, there was a station located there. Where there is a red pin, that’s where I made a contact. The maps don’t completely overlap, but it’s probably sufficient for illustration purposes.

And here’s a practical example: if, for instance, a station uses a 4×9-element antenna and 500W, its signal may be strong enough for me to hear even if the antenna is pointing elsewhere, but 25W on my end isn’t enough to make the contact.

Locator Map

This time I also heard a German station, and I was surprised by a station from Bosnia and Herzegovina, E71EBS. I was also pleased by the increase in Polish stations. If there were even more of them, it would be even better.

Missing VHF PA Multipliers

In the end, there were 61 contacts and 17 locators, which is fewer than a month ago. For example, locators JO80, JN77, JN87, and JN97 are missing. However, JN94 is a welcome addition.

Locator Map

Contacts by Country

http://www.opencontest.org/edi/map/20210719141307000098OTBCMU

What’s next? It’s definitely necessary to secure a reliable power supply so I can operate at 100W and R2CW. New antennas are also in the works. GL!

OM0AAO’s VHF PA Log

date	time	Call	Mode	Sent		Rec		WWL	claimed QRB	calculated QRB	2-way CC
210718	0803	OK4DJ	1	59	001	59	003	JN89FN	127	127
210718	0804	OM6ABF	1	59	002	59	009	JN99CH	42	42	✓
210718	0807	SP9RQH	1	59	003	59	007	JO90TC	174	174
210718	0809	OE6V	1	59	004	59	047	JN76XU	280	280	✓
210718	0813	9A1DL	1	59	005	59	047	JN85WF	418	418	✓
210718	0815	S59A	1	59	006	59	031	JN76XQ	296	296
210718	0817	OM6TX	1	59	007	59	015	JN99JK	80	80	✓
210718	0819	OK2OZL	1	59	008	59	013	JN89UE	30	30	✓
210718	0822	OK1KQH	1	59	009	59	028	JN79GO	258	258
210718	0825	OK1DOL	1	59	010	59	034	JN69OU	358	358	✓
210718	0826	OM5UM	1	59	011	59	009	JN98EO	52	52
210718	0828	OM3CQF	1	59	012	59	030	JN88RT	41	41
210718	0830	9A2AE	1	59	013	59	086	JN86HF	322	322	✓
210718	0831	OK2DTF/P	1	59	014	59	035	JN88VW	14	14
210718	0832	OK2VLT	1	59	015	59	035	JN99CS	90	90
210718	0837	OK2BUB	1	59	016	59	025	JN99EQ	85	85
210718	0841	OK1GI	1	59	017	59	017	JN89EX	160	160
210718	0843	OK2BMJ	1	59	018	59	017	JN89VC	19	19
210718	0846	9A3SM	1	59	019	59	061	JN85FW	357	357	✓
210718	0847	OM5LD	1	59	020	59	030	JN98AH	75	75
210718	0849	OK2CVH	1	59	021	59	025	JN89VJ	48	48
210718	0850	OK2RSC	1	59	022	59	012	JN89QH	57	57
210718	0854	OK2MAJ	1	59	023	59	023	JN89SG	45	45
210718	0855	OK2BSP	1	59	024	59	032	JN99AK	52	52
210718	0856	OK2VZE	1	59	025	59	044	JN89JM	104	104
210718	0858	OL70KRT	1	59	026	59	047	JN99BK	53	53
210718	0900	HG1DRD	1	59	027	59	084	JN86KU	250	250
210718	0902	9A2DM	1	59	028	59	041	JN86KD	306	326	✓
210718	0904	OM3CVV	1	59	029	59	016	JN88TR	21	37
210718	0905	OM4KK	1	59	030	59	016	JN88WS	5	24
210718	0910	OM1MJ	1	59	031	59	022	JN88PE	82	101
210718	0912	OM2ABC	1	59	032	59	002	JN88QA	96	115	U
210718	0913	OM3CPW	1	59	033	59	026	JN88OD	89	108
210718	0915	OM5ZX	1	59	034	59	019	JN98AP	23	38
210718	0919	OM3TFP	1	59	035	59	003	JN98EV	38	32
210718	0921	OM4AJH	1	59	036	59	007	JN88XR	12	28
210718	0925	S56P	1	59	037	59	103	JN76PO	313	331	✓
210718	0926	OM4AY	1	59	038	59	012	JN99FF	63	46
210718	0931	9A7D	1	59	039	59	075	JN95CI	386	404	✓
210718	0933	OK2TSG	1	59	040	59	072	JN99CR	105	86
210718	0936	OK2RAS	1	59	041	59	039	JN99FP	102	83
210718	0941	SN9W	1	59	042	59	073	JO90PP	228	209	✓
210718	0947	OK1KMP	1	59	043	59	108	JO70UK	239	230
210718	0950	YU7ACO	1	59	044	59	074	KN05RD	490	502	✓
210718	0953	OK2BSQ	1	59	045	59	024	JN89VS	107	89
210718	0954	OK2KPS	1	59	046	59	053	JN89WH	56	38
210718	0957	S57O	1	59	047	59	143	JN86DT	252	272	✓
210718	0959	OK1DTP	1	59	048	59	103	JO60VR	363	357
210718	1,000	OK1KKL	1	59	049	59	064	JO70PO	273	264
210718	1001	OK1KTW	1	59	050	59	068	JN89IW	151	140
210718	1017	9A0V	1	59	051	59	146	JN95PE	418	434	✓
210718	1021	9A7DI	1	59	052	59	054	JN85VQ	348	367	✓
210718	1026	E71EBS	1	59	053	59	095	JN94GR	457	475	✓
210718	1027	OK2KOL	1	59	054	59	042	JN99CN	87	68
210718	1030	9A0BB	1	59	055	59	204	JN85EI	401	421	✓
210718	1041	9A8D	1	59	056	59	179	JN95LM	376	392	✓
210718	1042	9A2B	1	59	057	59	063	JN75SL	411	430	✓
210718	1052	OM0RW	1	59	058	59	044	JN99RC	121	111
210718	1055	OK2KJI	1	59	059	59	099	JN79TI	175	175
210718	1056	OE3TFA	1	59	060	59	029	JN78UQ	160	168
210718	1059	OM2RL	1	59	061	59	072	JN88NR	56	68