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Testing

 

Here is the antenna mounted on a test pole I have on the balcony.  I took some preliminary measurements using by VNA as well as having some people from the CVARC ham club send some test transmission (Thanks for TIM-K6POI Todd-KD6RCM and Zak-N6PK for helping out). Since the impedance if 75 Ohms I tried a quick transmission but did not measure anything (only Tim was able to hear me on 2M).

 

Here are the results from the VNA on 2M and 70cm.

 

As can be seen the VSWR is very bad on these bands (as expected from the impedance mismatch). 70cm looks much better, but still not very good.

I also measured the received radiation while turning the antenna. Since this antenna has no encoder, I just placed 14 marks using a printout and moved the antenna until the mark was on top of these marks.  The signal strength was measured using one of the hacked UV3R I have, which I have output the signal strength in dBm on the LCD screen. Thanks for TIM-K6POI for transmitting for a couple of minutes while I wrote down the powers (I am working on some changes to the firmware to save these measurements).

Here are the results. Tim's station was 7.12889km away from the antenna at about 130 degrees to the antenna.

Angle	Test1@60W (dBm)	Normalized (dBm)	Test2@60W (dBm)	Normalized (dBm)	Test3@20W (dBm)	Normalized (dBm)
0	-104	-5	-105	-7	-112	-6
25.7143	-104	-5	-105	-7	-113	-7
51.4286	-103	-4	-104	-6	-112	-6
77.1429	-102	-3	-103	-5	-109	-3
102.8571	-100	-1	-101	-3	-107	-1
128.5714	-99	0	-100	-2	-106	0
154.2857	-100	-1	-98	0	-106	0
180	-103	-4	-99	-1	-109	-3
205.7143	-113	-14	-103	-5	-114	-8
231.4286	-115	-16	-108	-10	-116	-10
257.1429	-111	-12	-116	-18	-117	-11
282.8571	-109	-10	-114	-16	-115	-9
308.5714	-108	-9	-108	-10	-116	-10
334.2857	-107	-8	-107	-9	-115	-9

Here is a normalized polar plot for the 60W transmission.



Since I did not measure the power on a reference dipole antenna, I could not determine the gain correctly.
Theoretically, using Friis equation (taking the log to simplify things),  and a theoretical 2.15 dB half dipole, I should be getting -38dBm.

TX Power (dBm) + TX Gain (dBi) + (-32.44 - 20 log(Freq MHz) - 20log(Dist km) )  + RX gain (dBi) = RX power (dBm)
47.781513 dBm + 4.5 dBi + (-32.44 - 20* LOG(146.55,10) - 20*LOG(7.12889)) + 2.15 = -38dBm

Which is very far from the -98dBm I was getting. This is probably because of all the interference between us, so next time I would need to measure the actual received power on a dipole.