Testing Outdoor 2 meter Antenna

This is a 2 meter antenna i have temporary mounted outside for testing purposes. It is connected to long thin coax cable. With the coax-cable i can reach the vna connected to my computer. So i included it in the series of quick antenna tests.

See below the result:

Testing RH770 Antenna

 Also from AliExpress i got this RH770 Antenna

The length is adjustable so it is possible to do some tuning.

I did test it on full length.

Testing Abree AR771 Antenna

I also have 2 Abree AR771 Antenna's from AliExpress

They both look the same. See picture above. (Perhaps it are fake clones). Below the results of these two antenna's.

Testing another Aliexpress Antenna

Below the results of the measurement of another Antenna. 

I did buy this antenna some time ago on AliExpress.

Testing Quansheng Antenna

When testing the gate fence antenna (see a previous post) i also wanted to compare the measured result with some other antenna's. This is the result of a quick measurement of an antenna that came with of one of my Quansheng 2m/70cm radio's.

Gate fence electronics dismantling -2- Testing gate fence antenna

Testing a gate fence antenna with a vector network analyzer. This is a picture of the antenna of the original receiver for the fence controller after some cleaning. ( See previous blogpost)

As i have a vector network analyzer (vna) i wanted to test the antenna to check on what frequencies it can be (re)used. I soldered an sma connector to the coax wire, calibrated the vna and did a quick scan over a relative broad range.

See below the results displaying Smith chart, Quality factor and swr (VSWR). The lower the swr the better. The minima in the swr curve give an indication of optimal frequencies.

I also did the same quick scan on some other antenna's and post the blog reports with the results.  Therefore this blogpost is in fact part of two different series of blog posts.

-1- Dismantling the electronics of a gate fence. ( #GateFence )
-2- Some antenna's quick tested ( with a vector network analyzer (vna) ).

Gate fence electronics dismantling -1- Main control and rx board

In this post some pictures of electronics in a 220 Volt gate controller to control 220 Volt motors.After many years of service this device was not working reliable anymore and i needed to replace it. This blogpost is also to document the old situation.

Top left you see a transformer top right are battery holders (not used) . In the middle of the picture you see the main controller board. Also you  can see a part of the antenna. However this remote control was not used.

The cable bundle on the right form a separate circuit with cables going to a light sensor for a lamp.

In this picture the mains to the control board is disconnected .(The wires where temporary placed in additional screw terminals connected to nothing to put the fence control temporary out of service).

Original the connection was to the left two connections where also the white wire on the left is connected. The white wire is to power a 433 MHz remote control switch box (bottom left). From this control box go wires to contacts on the main controller board to external contact to open and close the gate. Below a closeup of the control board after disassembling.

On the right is the connector for the receive module. Below some pictures of this module.

As already mentioned the control board is completely replaced with a new (different) board. I also removed the antenna and tested it with a vector network analyzer. You can see the bottom part of the antenna in the first picture of this post top right.
Results of antenna measurements will come in a next blogpost.

Measuring Resistance of Fuses with a Milliohm Meter and Kelvin Clips -4- (Self Resettable fuse )

Recently i received this 30A self resettable fuse via AliExpress.

As you can see on the pictures on one side is printed:

A                        (i don't know yet what this means)

Suppl. Prot. 
LINE  LOAD (to mark te connections).

On the other side of the self resettable fuse has the tekst

ZHONGZUI 78 Series 30A
125/250 VAC 50/60 Hz  50VDC 
TC3OL1/U3

And symbols suggesting that the fuse had passed some tests.

And yes i tested it with my Milliohm meter by connecting the Kelvin Clips.

The measured resistance was only 0.002 Ohm

I don't know what the resistance will be under normal use contions, however is was happy surprised with this low resistance !!