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Reviews Categories | Antennas: HF Mobile & Accessories | MOONRAKER ATOM 20 Help


Reviews Summary for MOONRAKER ATOM 20
Reviews: 3 Average rating: 2.0/5 MSRP: $25.00
Description: Base Loaded monoband antenna, 160 to 10 mtrs.
Product is in production.
More info: http://
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DL4NO Rating: 3/5 Mar 24, 2011 03:26 Send this review to a friend
A Do-It-Yourself Project  Time owned: more than 12 months
In the meantime none of my Moonraker antennas are in their original state anymore. If you want to experiment with mobile shortwave antennas this is a good way to go. If you get a comparable Diamond antenna you cannot modify it without destroying it. But a Moonraker antenna can be easily dismantled.

For example you can unscrew the PL connector and remove the matching capacitor as I prefer to match the antenna by a 1:4 line transformer.

The upper diagram at http://www.techwriter.de/thema/kurzwel0.htm shows the Atom 20 in its original state and the lower diagram with a lower-loss inductor and an 1:4 line transformer. As you can see the resistive component of the feedpoint impedance is quite wideband. So tuning over the complete 20 m band can easily done with one or two switchable capacitors.

I still operate the 20m version on a Sirio PL-145 magnetic mount set on the roof of my car. My ODXs are Perth (OK, my partner was checking a CQWWDX contest station) and Quebec. During the last QSO I did some 100 km/h.

The 40m version was quite some dummyload. Rewinding the inductor with a thicker wire does not help as the coil is much to long already. There is literature that several ferrite rings on the fiberglass tube could help to shorten the coil length considerably. I experimented with a ferrite rod in the tube but could not find a rod made of suitable material.

About the matching problem described below: Without some kind of ground system you cannot tune any Marconi antenna.
 
DL4NO Rating: 3/5 Oct 17, 2009 08:00 Send this review to a friend
Simple Entry Gadget  Time owned: more than 12 months
You have worked VHF/UHF mobile and are wish to taste SW a bit while driving around? Then the ATOM 20 might be for you. This is one of the few SW antennas you can put on a mag mount like the Sirio MAG 145 PL. Mine has never come down for several 1000 km at speeds of up to 140 km/h.

This antenna is easy to operate, it is cheap. You can get your feet wet. But do not expect much more. Make sure that the bottom side of your mag mount has a conducting foil to maximize the capacity to ground.

Its strength also is its weakness: The antenna is some 20 mm thick. The fiberglass tube carrying the inductor has a 16 mm diameter. The inductor consists of some 40 windings of 0.8 mm wire wound without any distance from turn to turn and is 36 mm long. I did not try to estimate the Q - it cannot be much.

These losses are what makes the antenna easy to use: Its impedance is high enough that you might be able to operate it without an antenna tuner. For its length the antenna is quite broadband - some 150-180 kHz. This is enough for the more interesting portion of the SSB subband.

So buy one and do a few QSOs. See whether shortwave while driving is for you. Then consider how to improve your mobile rig. Getting reports some 3 S-units below of what you give is no fun in the long run.

BTW: If you wonder how to power your 100 W rig from the 12V outlet see http://www.techwriter.de/thema/mobil-st.htm . You might not understand the German but the schematic should be clear enough.
 
G0YAP Rating: 0/5 Nov 10, 2007 11:54 Send this review to a friend
Waste of time/effort  Time owned: 0 to 3 months
I needed a short antenna for 20 mtrs and bought the Moonraker Atom 20 at just over 1.3 mtrs long. It arrived the next day and looked ok. Mounted ok but when it came to tuning, I just could not get the SWR below 2. I changed the mount, coax, tryed a different vehicle and mount etc etc. not a chance! I borrowed a friends MFJ antenna analyser and it was not showing to be resonance anywhere on the hf band! Fiddled and farted about for 2 days to get it to work, rang Moonraker, they did not sound that surprized, sent me another, same! Rang them, they blamed the mount, me, the radio, the coax, the vehicle, the Russians, the weather,... I am returning it to them for a refund. What a complete waste of time, money and effort. The Moonraker advert in Practical Wireless states.. ' Atom..The Mobile Antenna,s that WORK'... What as.... a linen prop?? Buy one if you want, but clear it with the folks who hold the keys to your straight jacket first. G0YAP.
 


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