My current vehicle installation

After my first installation (details here) of ID5100 / IC7100 (swappable) in the vehicle I decided to have a HF radio permanently installed. Previously I had to remove the IC-7100 from the shack and put it in the car which was fine for long trips but not so good when I wanted to get a few SOTA contacts whilst out shopping on a weekend.

The Yaesu FT-875D is ideal as it is small enough and easily removed to take on a SOTA summit if the it's not too far too walk.

This is the view from the "cockpit":

Icom ID-5100 and Yaesu FT857D

And here is the messy installation in the back:

Back seat installation

A more detailed view:

The LDG YT-100 is an automatic HF tuner which is required due the narrow bandwidth of the vertical HF antenna.

The HF antenna is located on roof rack with short RF strap to the main vehicle body:

Don't be fooled by the aluminium roof rack - it is made of anodised components which have no (or very bad) electrical connection to each other or to the car body. Electrically this antenna only has the aluminium plate which holds the base and the strap to the car body. 

Although the RF strap is only 250mm (10") long, it's impedance is still a bit high for low frequencies (80mt + 40mt). This high impedance shows up when tuning the antenna tip - the tip is too short to get 1:1 SWR in the middle of the bands. The YT-100 tuner overcomes the SWR problem, but it does affect the  efficiency of the antenna.
If I take this antenna and put it on a chassis mounted base everything tunes up OK.

Nevertheless, numerous DX contacts to Europe (on 20mt with 59 signal reports) have been made from this vehicle installation. 

Vehicle Antennae

Driver side (left in this picture): UHF CB antenna
Passenger side (right in pic): 2mt and 70cm
Roof rack: HF antenna 80-6mt 

The HF antenna is the Amateur model of the Bushranger Multitap made by Bushcomm.


When I first started with digital modes fldigi didn't decode the way I expected it.

The problem was the radio output level was simply too high.
Digital modes are all about signal to noise ratios and not absolute signal levels

Screenshots on this page are intended to illustrate what signal level is required for fldigi to provide successful decoding.

This is a typical waterfall display on 14.070MHz. Take particular note of the background which has only a few background noise specs showing in yellow.
Adjust the radio output level and noise blanker until your 

typical waterfall
Typical Waterfall with PSK


The following image shows PSK signals which are too weak for reliable decoding:

PSK signal too weak to decode

Here is a PSK signal which should decode almost perfectly:

PSK signal with 100% decode

I came a across an interesting issue this week:

The installation:

Friendcom FC301D UHF transceiver connected via GMSK modem (Moencomm Starboard) to my Raspberry Pi hotspot running G4KLX software.

The Problem:

I have been using my Icom ID51A to work the hotspot for the last couple of weeks and had very good results. However, I found out that I could not receive audio from the hotspot with my ID5100 in the car, yet the ID51A worked flawlessly. The ID5100 would show a full strength carrier but refused to decode any data (calls signs or audio). In fact, the radio was switching between FM and DV, thereby indicating that the signal was not recognised as a D-Star signal.

Transmitting from the ID5100 to the hotspot worked OK, but the ID5100 could not decode anything transmitted by the FC301.

At first I thought the FC301 might be transmitting slightly off frequency and the high selectivity of the ID5100 is responsible for the issue, but the spectrum analyser confirmed the radio was on the correct frequency.

The Solution:

The FC301 has a setting called "Band Control" and further investigation revealed that this setting was on 12.5kHz which should (theoretically) be sufficient for a signal that's about 11.5 to 12kHz wide. A quick change of this setting to 25kHz and the ID5100 was decoding fine - Culprit Found - the bloke who programmed the FC301 (ME!).


According to the FC301 service manual "Band Control" selects between the wide band and narrow band ceramic filters which are part of IF amplifier and it's purpose is to "eliminate unwanted signals before amplification" and to "filter useless spurious signals". 

The spectrum screenshot below shows the difference in signal between the narrow and wide band mode:

I'm no expert on RF so the only thing I can see is the small humps ether side seem to be a little bit lower in narrow band mode.

Here is a comparison with an Icom transmission:

I note that the small humps on the ID51A are even higher than the FC301 in wide mode.


The main aim was to fix the problem, and I have achieved that. My current level of knowledge is insufficient to draw a final conclusion but maybe someone else can come up with a good reason why this problem occurs. If you have any suggestions please email me on vk3erw AT gmail DOT com.

Post Script (26 Sep 2014):

The reason for this problem was the low output level from the GMSK modem - See this article for detailed information.

Thanks to VK3ASC for contributing this article.

Mac version of FlDigi with FLRig configuration, via USB cable to connect the IC7100.
FLdigi and FLrig can be downloaded from

FLdigi, under configure> operator> Rig tab, Deselect Hardware PTT, Rigcat, Hamlib if selected and only select Use XML-RPC program.


Flrig, under Config> Setup> Transceiver, Select the IC7100 in the transceiver list and select PTT via CAT
Ser. port you select the USB driver. You can download the Mac USB driver from

Select NONE in the PTT Port field.


IC-7100 settings:

Under Connections

USB MOD Level: 10% (This Article explains why)
CI-V Baud rate: 19200
CI-V Address: 88h
CI-V Transceive: OFF

Must have USB-D or LSB-D selected on the transceiver operating mode for it transmit your digital transmission.

You should check your RF signal as described in this article.


Manual Icom Tuner

Many Icom radios (e.g.7100) have a connector for automatic tuners such as the Icom AH4. The cable supplied by Icom is of a fixed length (10m) and is not shielded. Icom recommends to use shielded cable for any length greater than 10m.

The cable is nothing special and doesn't carry any RF or data signals but if run unshielded and in parallel with a [possible radiating] feed line I would assume that induced currents can cause all manner of problems.

In my particular installation ( Long wire and AH4 tuner ) the cable length exceeds 10mt so I decided to get a good quality industrial cable with braided shield. The cable was fairly easy to come by but the connector is a little bit more specialised.

I ended up finding a suitable connector on ebay. It is called "MOLEX connector set - Standard .093" 4 way (4 circuit) 1 x 4 Line" and is sold by a UK based ebay vendor. The price is very reasonable and includes freight.

Molex ConnectorManual Icom Tuner
Molex Connector kit