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Nagoya REVEX NA-660S Gooseneck UHF 400-470MHz SMA-Female Tactical Antenna

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You were not clickbaited it is official name on Aliexpress 🙂
If you wondered how this antenna performs how is its SWR or what is hidden inside fiber-glass tube check the pictures below. Teardown of antenna is irreversible process beacuse everyting is glued together.

The antenna with reverse SMA on Zastone M7 radio.

I dont know how manufacturer measures the antenna or if this design is one of that “dualband” because the resonance frequency is somewhere between VHF and UHF band but it looks like 300 MHz is a sweetpot.

NanoVNA measuring Revex antenna.
Partially diasambled fiber-glass tube.
Sleeve-dipole antenna inside.

Inside the antenna there is very interesting combination of sleeve monopole (counterweight) with normal mode helix as radiator. Further investigation of antenna will follow next time.

There is antenna specification from seller on Aliexpress:

Brand:REVEX (Nagoya)

Connector Type: SMA-Female

Frequency: 400-470MHz (400-470MHz will be better signal)

Gain: 3.5dBi

Max Power: 20Watts.

V.S.W.R: Less than 1.5.

Impedance: 50ohm.

Antenna length:330mm

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Meander dipole antenna

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It took some time from my first design on meander dipole antenna, but last weeks I made further progress. Meander dipole is electricaly same length as dipole antenna but meanders make it physically shorter and they are able shift impedance to the sweetpot of Smith´s diagram.

Fig. 1 – Antenna overview.

Big advantages of meander dipole antenna is near-perfect impedance match to power line and smaller size than physical. But of course there is disadvantage in lower radiation efficiency.

Meanders vs Relative Length
Fig. 2 – Number of meanders vs. length reduction.

It looses about 8-12 % of efficiency which can be 0.7 – 1.2 dB which looks horribly but it certainly nulls the loss on full dipole because of impedance mismatch 73 + 43j Ohms to 50 + 0j Ohms.

Further development was made on implementation of SMD baluns. Previous experiments with various types of ferrite rings were not successful. I discovered cheap wideband SMD made by MACOM [4] which is rated to 250 mW only. But if you dont mind over saturation of core it can work up to 4 W without heating HI.

Model was made in AntennaDesigner toolbox from MATLAB. You can see that simulation of Impedance in Fig. 3 is nearly perfect antenna.

Fig. 3 – Impedance of meander dipole antenna.
Fig. 4 – S11 parameter.
Fig. 5 – Radiation pattern.
Fig. 6 – PCB visualisation
Fig. 7 – Measuring S parameters on NanoVNA.
Fig. 8 – Balun placed on meander dipole PCB antenna
Fig. 9 – Trying to make rubber duck / donkey dick anntenna with meander dipole inside.
Fig. 10 – Final result looks better than it worked.
  1. https://www.mathworks.com/help/antenna/ref/dipolemeander.html
  2. https://www.qsl.net/kk4obi/Meander%20Dipole.html
  3. https://apps.dtic.mil/sti/pdfs/ADA617035.pdf
  4. MACOM / MABA-001759-000000
MABA_007159_000000-318068Download
meander_dipol_280M.kicad_pcbDownload
Shorts

Hamshack #2

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There is short update on building my hamshack. I was working on walls and last night I laid the floor. Before weekend I’d like to finish all flooring and start placing furniture.

OSB mudded with KANUF Uniflot – originally for drywall
First coat of prime with just a little paint to see where it was coated.
Spruce plank with sides formated on 45 deg to fit into corners.
Second coat of paint and corners being painted by primer.
Measuring vinyl floor plates for minimal waste cuts and 2mm mirelon underneath.
Final result with just some details waiting to be done.
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Maidenhead Locator System

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Have you ever wondered how the so-called QTH Locator or WW locator is calculated and what is behind it?

Many HAMs and radioamateurs use it but ask them where their locator came from and not many can tell you. There are plenty of web based applications which overlay Google maps with a locator grid and many of them provide a calculator for conversion from other geographic coordinates to Maidenhead Locator System.

clear all;
close all;
clc;

m = mobiledev();
m.Logging = 1;
pause(2)

lat = 50.2727514;
lon = 14.2518494;

alphabet = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','R','S'];

locator = [];
len = 4;

lon = lon + 180;
lat = lat + 90;

lon = lon / 20;
lat = lat / 10;

for i = 1:len
    
    lon_tmp = floor(lon);
    lat_tmp = floor(lat);
    
    if mod(i,2) == 0
        
        locator = [locator int2str(lon_tmp) int2str(lat_tmp)];
        lon = (lon - lon_tmp) * 24;
        lat = (lat - lat_tmp) * 24;
        
    else
        
        locator = [locator alphabet(lon_tmp+1) alphabet(lat_tmp+1)];
        lon = (lon - lon_tmp) * 10;
        lat = (lat - lat_tmp) * 10;
        
    end
end

locator

Corresponding output:

locator =

    'JO70DG05'

And the most amazing aspect is executing .m files on your iPhone. The disadvantage is that an internet connection is necessary for computing via the application.